I probably suck at making vanilla levels, but maybe my previous entry in this contest will give me some ideas. Maybe I'll do better than I did last time. (Cursed FG/BG initial settings...!) I have quite a few questions about this, though. You did say that as far as ExGFX goes, ANYTHING that was in the original SMW is okay? Does that include rotated (not flipped) tiles? Also, where will you draw the line for hex edits? Some of them aren't really ASM hacks, but...simple stuff like changing sprite tilemaps and boss HP is okay, right? (I could do a very complex series of hex edits that would add a JSR or JSL to freespace in order to do something like make the Koopa Kid bosses teleport you instead of ending the level, for example, but that would definitely not be permitted, would it?) And do levels with side exits enabled count toward the two exits? Finally, is the No Sprite Tile Limits patch in the list of allowed patches? That could have fixed half the problems I had with my last entry.
I'm working on a hack! Check it out here