My List: (in no particular order)
 1)  Gnomes that have a decent paint job!!! 
 2)  Gem dragons
 3)  Stirges
 4)  Vermin swarms (A whole bunch of tiny, a whole lot of trouble) 
 
 5)  Driders
 6)  Giants (of all types)
 7)  Vampire
 8)  Bears (and not celestials or fiendish)
 9)  Mounted figures (Fighters are great and all but a Paly needs a horse!)
10)  More lizardfolk poses
11)  More Draconians
12)  Hydra
13)  Female gnomes (so far all they have made are males so this is different than #1)
14)  Ankheg
15)  Cloaker
16)  More goblinoids
17)  Scorpions
18)  Centaurs
19)  Black Scale lizardfolk
20)  Aboleth
 
Siege weapons, treasure, dungeon dressing would be awesome, but I don't see it happening, all of those already exist and don't really support a minis battle format (ok seige weapons do, but they would already have crew figs attached or worse the weapons are VR and the crews are all C.)