First off, I trust Raven to come up with some really creative and original alien enemies. Hopefully they will do the same with some of the buddy allies that have been talked about.
I agree with a lot of the other suggestions already mentioned - although it would be a tall order to include them all.
My own picks would be...
A War Beast of Onderon
Of course, they would all have to be resurrected, but I like the look of them in the Tales Of The Jedi graphic novels.
Mostly, I hope that Raven give us a good variety of different species to interact with - from rat size all the way up to AT-AT size. ;-)