Mites are great for low level villains, and I was going to suggest gnolls but someone beat me to it.
I once ran an entire campaign around one villainous race I retconned to D&D -- Skaven. With their different clans and Moulder-bred beasts of war (you could use dire rats, advanced dire rats, and reskinned owlbears work very well as rat ogres), plus the magic of the grey seers (with rat familiars, natch) -- well, it was a fun campaign.
Oh, and 3.5 Warlocks can be adapted quite nicely into the warplock engineers of Clan Skryre.