In this thread, I will be covering a wide variety of things that could be done in the Arcade to give it that extra kick we've all hungered for ever since beta ended. The Arcade is our source for the widest variety of assets in the Spiral Knights universe, why not give it a little extra love?

Step 1: Increase the chances of a Scenario Room appearing in any given level by a considerable amount.
Step 2:

Burning Wolver Dens
In which Ash Tails and Vog Cubs reside. The ground is charred beyond recognition, and lava tiles are scattered across the scorched wasteland.
The cliffsides are similarly charred, with occasional holes for an ashtail to peer out of.
The floor has devilite-sigils on it, colored orange and largely following a spiral pattern. These become more common (and larger) as the Tiers progress.
The occasional Red Rover is present throughout the level.
Rarely, an Ironwood Sentinel will spawn.
Silkwings that appear have a Volcanic coloration.

Frozen Wolver Dens
In which Frostifurs and Skolvers reside. The ground has been snap-frozen, and Knights slide across frozen areas. Bushes have also been frozen, and require three hits to break.
Blue devilite-rune spirals are present, following the same pattern as the Burning dens.
Rarely, an icy-colored variant of the Ironwood Sentinel will spawn, with frost particles emitting from its head.
Silkwings that appear have a Polar coloration.

Random Event: Apocrean Abduction!
The Apocrean Harvester's "surprise" attack at the party button isn't all that surprising if you're expecting it.
In Tier 3 Undead and Fiend Clockwork Tunnels, stepping on "progression" party buttons will have a (rare) random chance to suck the player into a different level at depth ???, being a dark Arena with violet-colored torches and a Graveyard tileset. This Arena features two wide rooms, each containing a standard assortment of Undead and Fiend monsters.
However, at the end of the second room, the player(s) must also fight an Apocrean Harvester. At the end of the second room, a circular assortment of Crowns is dropped in the room's center, along with three Grim Sparks in a triangular fashion.
Upon taking the elevator, the player will arrive at the depth directly after the one they were taken from.

Scenario Room: Turret Trap!
This takes place in a Scenario Room (Gremlin and Construct Clockwork Tunnels). A 5x5 arrangement of Green Treasure Boxes is in the center of the room, with pedestals around the room. Upon nearing the boxes, a gate behind the player closes, trapping them. The pedestals spawn three Rocket Puppies at the three open sides, two Red Rovers beside the Rocket Puppy at the far side, and a Sick Puppy, Sparky, Slush Puppy, and regular Gun Puppy beside the other two Rocket Puppies. The player(s) will have to defeat all the enemies for the gate to re-open. A number of Forge Sparks will apppear at the spot where the trap gate was located, one per Tier.
I'm a sadist.

Scenario Room: Snarbolax Cubs!
This Scenario Room occurs in Beast levels, being a heavily forested area with a clearing. In this clearing, two stunned-type mini-Snarbolax will appear, albeit without the Stun status. They will be vulnerable to attack, but possess the same moveset as a normal Snarbolax.
Upon their defeat, a number of Primal Sparks will appear in the room's center, surrounded by a moderate amount of Heat and Crowns.

Random Event: Fraternal Firefight!
This event occurs at an alternate type of "progression" button in Gremlin and Construct Clockwork Tunnels. The button area is wider, with a roarmulus twins-style switch/wall configuration.
Upon stepping on the button, two miniature Roarmulus Twins will ascend from the sides of the room. A watered-down Roarmulus fight will commence (no lasers or air-to-ground rockets, only one stage), and the gate will open once the two have been defeated. Defeating the first Twin renders the other vulnerable. A number of Forge Sparks, one per Tier, appears once the gate has opened.

Random Event: Snipe Flight!
Appearing randomly anywhere they can fit, a flock of Snipes will swoop down by the player(s) and stay there momentarily before flying off.

Random Event: Wandering Soul
Appearing in Undead levels, an occasional Freed Soul will float by, not taking notice of the player. Occurs more frequently in Graveyards.

Scenario Room: Ferris Cog
A giant Clockworks gear that has ferris-wheel-styled buckets on it that will "carry" a Knight to a higher/lower elevation, with the rest of the level continuing at that elevation.

More Buckets.
more buckets pls

Re-introduction of Blast Jellies' full power
Blast Jellies aren't as much fun as they used to be since their initial explosion was neutered. This is a petition for their restoration.

Cursed Graveyard
A rare variation of Graveyard that features a 1/2 chance for Carnavons to spawn in place of Dust Zombies. The entire level features a purplish background haze, similarly to Legion of Almire's second floor.
Deadnaughts occasionally spawn.
A single Grim Spark is present at the elevator.

Random Event: Dead Railway.
Appearing as an occasional "extra" to Undead levels, the Ghost Railway from Moorcroft Manor can be seen, with an occasional wooden push-cart rolling across it.
The cart is controlled by two Zombie Bellhops, and has luggage stacked across it. The cart will either:
1) Rattle around due to the railway's uneven surface, with luggage sliding around the cart. Luggage occasionally falls off and reappears on the cart moments later. The two bellhops occasionally utter a phantom's laugh, with purple "laugh" emote particles. (rare)
2) Smoothly glide across the rails, with the two bellhops maintaining a quiet, mechanical rhythm. They will do nothing upon proximity to a player. (common)

Random Event: Stranger Carriage
On occasion, a Stranger wearing a pack may float by on a modified Elevator cage. This cage is attached via strings to a large, Snipe-shaped balloon of random color. May occasionally attach to a level upon spotting a player, and offer them various goods in exchange for Crowns, including Minerals, Materials, Usables, Pickups, and Vitapods. May also rarely sell Stranger costumes and accessories.

Random Event: Crash Pod!
Appearing in any Arcade level, a Crash Pod may slam into the ground, causing moderate damage to enemies in the area and quite a bit of screenshake.
A dazed Recruit NPC (Breaking in the Recruits-type) will open the hatch and join the party until the next elevator.
Another variant of this may appear in which a Crash Pod shoots down into the Clockworks past the level. A loud bang can be heard some time later, along with a parachute regiment of Scarlet Scouts descending the same path as the Pod.

Random Event: Lichen Meteorite!
Following the same behavior as the Crash Pod, a burning Lichen Meteorite will slam into the ground, dealing damage to any present enemies. Lichens sufficient to form a Giant colony will emerge in their smallest states moments later.

Scenario Room: Frostbite
Occurring in Freeze levels:
On occasion, a band of shivering NPC knights can be found around an unlit fire. Attacking it with a Fire-dealing weapon will light it and grant the player health.
A variation of this can be found with a fire pit but no wood, having been stolen by a pack of [monster name]. Donating Driftwood materials will grant a lit fire and health regen.

Particle Addition: Zombie Soul
Upon the death of a Zombie, a small wisp of light will emanate from the spot where it died, lingering a small moment before vanishing.

Impostocube Slime Coins
Impostocubes altered to drop 1 Golden Slime coin 100% of the time, for obvious reasons.

Random Event: Bombie Rush!
Appearing in Undead Clockwork Tunnels, this Scenario Room involves a standard arrangement of Treasure Boxes, and eight Bombies that spawn upon a player getting too close to the room's center.

Level: Cryptic Statuary
While not an exact copy of Arkus' Statuary, I'd like a level designed similarly to it. It has a certain atmosphere unseen in most places in SK.