Terrain is going to be a big thing. My friends are both working on it, one will do something then the other improves, and Whitehorn had offered to pop over it a little, so eye candy shouldn't be a problem.
What sort of ability choosing system did you have in mind? Because however much I would like to add one unless they are done extremly well(I know I can, just don't know if I am not too lazy to try) they end up looking lame. Plus they eat up a lot of extra and mostly useless hero abilities.
Creeps should be more than cannon fodder. Caster's will have minor auto-cast abilities and such, so keeping them alive will help you take out a lane and fight other problems that arise.
So far I also know there will be controllable "nodes" that can be captured to give a myriad of bonuses, from creep improvements to the ability to hire mercs or maybe waygates for easy transport.
Suggestions, comments concerns?