I have slightly longer post by pro, wrote this before he did his post. Anyways here's my view on this.
I'm not sure if anyone whos been doing speedrunning or hunt mode a lot has tried levels before (I'm not nether of them in any high level) but from looks of it some of them need some slight changes and improvements. Not in interior quality way but in gameplay and layout way.
Here's my thoughts (Note they are based on what I see in images, everything may or may not be the same if i would play the actual level so take my criticism with a grain of salt):
Block tower: can't see whole level so hard to judge but it seems like level is accomplishing it's original intentions, though I suspect one tiny annoyance with marble spinning and launching itself off platforms.
Champions road: I'd say best one from the bunch, can't say anything much, I would actually be looking forward to play it. Only way this level could go wrong is if any of the challenges are really tricky to execute, have some major annoyances.
Hazardous ascend: Looks like something taken from CLA level pack. I mean sure I get the idea, it's just horribly executed. By making a wall of hazards and stretching mines you don't make a hazardous challenge, you just make a wall of hazards. Usually the way you know you've placed hazards wrong is if you can't get through them or avoid them by rolling. If there's some jumping challenge in between then until you reach that jumping challenge IMO you should be able to get to it by rolling.
Whatever goes up: looks good, should also play fine.
Colorful nation: I'm confused by this layout. I see what has been original intention here but it just went wrong. Just by better gem placement this level would be improved a lot.
Epic sprawl: I have nothing to say much about this since I can hardly understand all pathways but I'll just tell why I think original sprawl as map is so good. Sprawl's main layout is 3x3 square. From any of the the sectors in that square you can get to different square quite easly by eather using fluid pathways or if square is blocked off more than the others, there's powerups or higher land that helps you reaching it if utilized with skill. Yet there are still some places left that eat your time if you fail. There isn't overwhelming amount of powerups aether, it's balanced. Basically just slapping architectural peaces of sprawl together doesn't make a good hunt level. It's the layout that does. I'm not saying your layout is bad, i can see lot of good things in it but I see some possible issues too.
Half pipe fun: Can't say much until I play it, there are some concerns I won't mention because they are just speculations.
If gems are placed correctly though and you can collect them one after another if executed properly, then this level has potential.
Folley: Hard to tell anything from image, if this is hunt level then symmetrical layout imo isn't the best. Getting around map looks odd too. The reason why for ex: ramp matrix works as hunt level is good gem placement lower and higher ground and powerups that allow you to scale map easily and backs up huge height difference.
Centroid: interesting and promising layout/idea. Powerup placement in some places makes no sense. Teleporters idea is good, I would place them in different places though. I expect I would fall obb a lot, then again this advanced hunt level.
You guys need someone who can give you good constructive criticism. Someone outside of current mod team that can test it and say with fresh perspective what he/she thinks is wrong and good. When you make a level and play it ask yourself: Is this fun, is this layout creative, [optional] can I come up with more than one way to execute the level. If there is challenge that is plain annoying to you then it will certainly be annoying to everyone else not talking about less experienced players. There is difference between fun, challenging and bad, annoying. I have scrapped few of my maps because they felt too hard or it they weren't playing that well in past.
To sum up what I want to say with all this is: Don't let your mod turn into MBEmerald which had lot of levels but was forgotten fast. It wasn't bad mod, it's just people didn't enjoyed it much. I believe with some improvements it is possible to make your mod a lot better. Remember that core of any good mod is good gameplay. Graphics come second and currently graphics for your mod are perfectly fine. What all of you should work on most now is polishing gameplay.