Alright, here's what i believe to change. (I'm only noting all mine because like, the more people who ask for something, the greater chance it happens. With requests. :P)
So, let's begin.
First, i actually want the OLD sprites back, from 1.09.4. The new sprites don't really fit SRB2's style, imo. Especially Eggmans. Even more especially the Final Eggman Sprite.
Second, I think you should attempt to remove CEZ 1 + 2's lag. It's affecting my server and people blame me for it. >.<
Third, i would like the old Tag mode back. :P With the new modes, so there'll be three.
Moving on to No. 4, which i actually want the MOST...
UN-CROWD THE LEVELS. >.< (Except Red Volcano.)
The levels are too crowded now and don't feel like SRB2 at all. I want nice and open-er levels like SRB2 1.09.4 or the Mystic Realm, not these crowded bits. It fits Red Volcano, though. :P
And finally, some console variables.
allowchangeskin - I don't know about you, but i actually want this for some reason. It should allow the person to choose at the start, but not after. It should add some challenge into other servers. (As people just go 'OMG i cant get here as Sonic i'll switch to Tails so i can get through.' >.>)
banip - Wait a moment, already said. Well, I WANT IT TOO! (I also want the kick/ban reasons, curse filter, visible crosshairs.. but not the Team-Auto-assign for CTF. Yes, these were all from the above post. :P)
I also want a more organised 'Help'.
...Aaaaand, that's about it. Those are my suggestions of what i want in SRB2. :P
EDIT: Wut, the above post dissapeared. o.O
EDIT2: Thought of another one.
Skidding - Like in official games, if <character> RUNS in a direction, then immediately presses the other direction, they'll skid to a stop quickly, then walk in the other direction. (Mainly for 2D mode. :P)