Recommendations for a veteran knight?

Since I've started playing well over a year ago, I've achieved quite a lot ingame. I've done nearly every piece of PvE and PvP content available, and have become proficient at them. My arsenal is essentially complete, and I don't want any additional pieces of gear. Now, I'm not sure what to do in this game. I now have all the things I wanted to have when I started, and have done the things I wanted to do. Things are starting to get a bit boring now, and my performance is restricted more by my extreme lag than a lack of skill on my part, making pvp lose much of it's appeal.
So, any recommendations for what I should do next? I'm really at a loss, because nothing in the game seems to be particularly interesting or challenging anymore.

With a crown/ce total.
Choose a number that seems slightly out of reach, then work your behind off to get there. 20m was my mark.
Its amazing what you can accomplish once you dedicate yourself to it :)

do what a lot of others are starting/have started doing; challenge yourself. Proto everything? Sure. Shadow sword vana? F*** yeah!
Just do the ridiculous/unusual stuff thatmost people would never do. Adds that unique twist to overly played areas.

Do PUGs, soloing isn't really fun. Arcade @ full party IS FUN INDEED. Start using those minerals you hoarded & built gates you want!

Well, even with my absurd lag, I can go through many levels (on solo only, due to even more lag from parties) without being hit. Proto runs sound alright, but I expect to die only because of lagspikes. It'll certainly make me more careful though, I sometimes don't play very conservatively, instead going for dps, or derpiness.
I think Rommil's idea is alright, maybe I should set a goal. Though I'm not exactly sure what to do with 20 mil crowns, never mind CE.

Though I'm not exactly sure what to do with 20 mil crowns, never mind CE.
Punch says hi

Stick around Advanced Training Hall, wear your flashy 5* gears and use your various weapons. Sooner or later a newbie would come up to you complimenting your arsenal, or send you a random friend request.
Accept it. And try to convert/train this newbie into a veteran just as you are.
Some of them have the potential, some will make you rage. Can you convert them all? That's the challenge.
Alternatively, do that in front of Auction House and try to reform beggars into useful members of the community.

pretty much, lol.
sprinkle aura x2
vh ctr gran faust
vh ctr freezing vap
vh ctr fiery vap
vh ctr blaster
vh ctr pulsar
vh ctr hot edge
vh asi hot edge
vh ctr + med asi brandish
vh ctr calibur
vh ctr sealed sword
prism hat x3 (got a good deal on the other two, lol)
prism blowout x2
prism mecha wings
lots of locked double rolls--aiming for med asi or better on all my vh ctr gear
giving random stuff to pawn
buying low-end accessories and gifting them to friends
buying a white tabard and holding it for divine-blade until he gets enough
lots of single rolls
and buying up various other rare accessories and forgetting what i bought.
yeah.....thats about it.

Playing with friends makes a big difference. My guildmates and I occasionally do runs where the sole objective is to blow each other up as many times as possible while still finishing the level. (think exploding blocks, shield bumping lumbers mid attack, etc) Normal missions tend towards the "kill everything and move on" mode- try to make your own objectives within levels! The lumber challenge is fun. Other options include having as many health capsules / totems at the end of a level as possible, or using alchemers to shoot around corners and play levels out of order.
But if you want to do more than collect, bring friends. I could see a good game of capture the flag coming out of a deconstruction zone or courtyard vanaduke level- mayhaps using keys or totems as flags, and shield bumping zombies to contest territory? You'd be surprised what a well placed nitronome can do to disrupt someone's shield timing. ;)
It sounds like you're happy with your state of completion outside of levels, or else I'd suggest goals like collecting every recipe and maximizing your UVs. That can feel grindy rather than creative, though.
Changing playstyle while keeping the goals more normal is of course also an option: Try the same levels with different load outs and explore possibilities- all guns, only one weapon, whatever.

"Though I'm not exactly sure what to do with 20 mil crowns, never mind CE.
Punch says hi"
So does my wallet, among others.
Jks, I don't need it so much. Not anymore at least, thanks to a certain SOMEONE quitting the game before returning.
I still haven't actually spent the stuff he gave me, I just built up on it and spent what I built up.

Come back when there's new content.
Boring suggestion, but I think that's really the best way not to get burnt out on a game.

Haha, when exactly do you guys think significant new content will be released? I don't really have high hopes.
Maybe I should play with my friends more, that probably helps.

I guess I'm more or less in the same case as you. The Lumber challenge was fun but relatively easy to do. I did the Trojan Challenge too, but again, not that hard being 2 (tho doing it alone should be a worthy challenge. I doubt I can do it easily).
I also like the idea of trying to make new players veterans. Tho playing in T1/T2 to help them seems boring. Perhaps I'll give it a try.
As for new content, danger missions were announced a few days ago. As usual, we don't have any definitive date, but I'd bet for less than 1 month. Nick said it should be a real challenge even for veteran players. That's the thing I'm looking forward to.

Did you already solo all the shadow lairs? I find it to be really funny :D
How about a challenge like the Lumber Challenge?
Or maybe a few quick runs in the Arcade?
Or some Gauntlet?
Maybe all the Shadow Lairs?