SO far all the floating isle levels, lichenous lair, aurora isles, emerald axis, all use the same grassland-esque tile set, which is great, it looks good, but im going to suggest an alternative, well actually two and reference one of my older threads while we're at it.

so first thing why not bring a bit of variety to floating island levels with a new tile set, nothing overly fancy more just a re-skin and some terrain models

my idea, the first one, is to have a desert/arid wasteland kinda western tile set based on the floating island one. hey we've already got the gunslinger set - lets give our cowboy wanna-be knights somewhere to look rugged and walk off into the sunset - stetson clearly silhouetted against the dyeing light of the setting sun.
first change is remove grass in favor of sand, the dirt can remain the same(a recolouring would be better of course as its just meant to be compacted sand)
re-skin the destructible grass to be more yellow/brown - dying
trees which scatter some of the islands are replaced with jutting red rock (i'm australian, that's the colour of the rocks in this country, perhaps a different colour would be better) or with giant cacti

the stone walls and pillars which scatter the current tile sets could easily be replaced with palisade walls , the low stone walls with wooden fences.
the bones from undead themed levels wouldnt look out of place in a desert setting either

as far as visual effects for the area (the grassy isles have leaves which blow about) tumbleweed and/or dust swirls would look nice

Now about that sunset - heres the second idea - currently all floating island levels are either day light, or night time. So how about a twilight (the time of day not sparkly deceased hufflepuffians) lighting and background
Then our knights can ride(the elevator) off into the sunset - very dramatic
This way you can effectively add 4 entirely new level sets - floating isles twilight, desert isles day, twilight and night

Now we all know you cant be a cowboy without horses or shotguns (well you can but it just doesnt have the same kind of flare) - horses aren't happening so get over it but shotguns like this would be cool - though admitedly entirely unrelated to the content of this thread