I'm sorry I couldn't submit anything for this contest. Instead, I'll just vote on the single player maps for now.
Icicle Warehouse by glaber - 2/10
I don't know about you, but I play SRB2 to get some challenging gameplay, not to run through ugly hallway collections like this. I mean, this level just had no challenge whatsoever, aside from some annoyingly placed enemies. Speaking of enemies, why did you replace the Buzzes with those recolored SRB1 enemies?
However, there were some other noticeable flaws aside from the bland visuals and there being no challenge at all: the 'storage room' is a dumb secret, because it had too many powerups for such an easily reached area. And of course, the inescapable tunnel. Seriously, how did you miss that? And why did you add that weird wall?
Luckily the level wasn't all that long to begin with.
Flooded Mines by Spongecar - 1/10
I'm sorry, but this level is just plain garbage. It's way too short, it's really ugly, there are no multiple paths to speak of, and the end is horribly unclear. Reverse gravity doesn't fit in a mine/GFZ theme to begin with, but I really expected to be able to jump and not suddenly get reverted to normal gravity. If you had chosen something else than spikes, a hazard that is normally jumped over, it would've been better and maybe more clear. Like the previous map, I was happy to see that it was extremely short, which is not a good thing.
Twilight Isles by Thompson - 9/10
Well, this is certainly a nice change from the previous two entries! Not only is there a lot more to comment on, most of the content is actually really enjoyable! The beginning was quite confusing at times, and the sky and music seemed unfitting to me, but much to my surprise this level became better and better as I neared the end. However, that doesn't mean that it's flawless: the rock crusher after the first checkpoint seemed quite surreal to me, some Buzzes and Crawlas were placed in rather annoying ways, one spring in the waterfall room can launch you into a death pit if you're not careful, and the hang glider was quite slow with moving downwards. Otherwise, this is a really solid level.
The water skipping area was incredibly clever, the turret room was quite a lot of fun, the hang gliding segment was difficult but awesome, and the ending was well-made too.
EDIT: I just discovered the mushroom path at the start. It is infinitely better than the other path, which was already really fun, so you get one point extra. I mean, it looks better, plays better, and has more creative ideas and gimmicks.