Ok Roboegg. I have a couple (or more) suggestions for you.
1.) Don't start, continue with, or end projects without proper experience. If you are still learning, all you're going to get is, "Blah blah blah blah bad, blah ring placement, blah blah blah items, blah blah blah design, blah blah blah you suck." I suggest you start slow, and go with your own pace, because frankly, you showed you had potential with your Egg Factory map in Jmankart.
2.) Practice making all types of maps. Don't make the thok barrier's walls too high (4096), and use FOF's. Try to figure out how to make different specials with the SRB2 Specials List. It's an excellent reference, and helps me out too, when I need a bit of refreshing. Match/Tag, CTF, Circut, Co-op, and the unofficial type, diver, should all be recognised, and each one is put together differently.
3.) Item placement is a large part of the map's playability too. Fifty (50) invincibility boxes in the same area is bad. This doesn't seem to be a problem of yours, but it should still be part of your list. Remember, rings make SRB2 go 'round. Use patterns. Don't forget to use more rings for multiplayer modes, such as Match or CTF. You shouldn't use random boxes in Match or CTF though, instead, take a silver ring box, and set the deaf flag for that box. It won't be random, but the items will be different each time opened. It acts like a random itembox, without the random icon, and each item has a set chance of being hit the next time after the one before it.
4.) After completing the basics, you should work on appearance, and scenery. Even if a level has really good gameplay, if it looks clunky, it won't be the best choice for netgames.
5.) Pretty soon, when you get extremely good at level wadding, you need to start calculating the size of the textures, and how many units they take up for the best appearance possible. The professional maps work that way. Take CEZ for example. Ever notice how perfectly the bricks are alligned?
Try following tutorials if you can (hell, I might just make one too), they should help, and I hope these tips helped too.