Lady E (I think it was Lady E) has some great demon resources. Some of which are quite large.
Currently, they cannot be downloaded from her site, but many of these can be found in the Horror Mod. (on PES)
I'd be careful about what you use from the above mentioned Giants.
I don't like Giants very well. It's nothing extraordinary and kinda dull.
I played the Horror Mod and the only demon thing I saw was the Demonite, which is scrawny and more zombie-like than anything. I'm thinking of a fierce demon as in Balrog fierce. Something which races very rarely accomplish.
@Yombie:
A Cthulhu would be cool and I would do that, but that's what I'm LOOKING for, some resource that would offer something that menacing. Haha. Just for future reference to everyone, I cannot edit meshes. Have not the patience or anything for it. Modelling just isn't my thing, I guess.
I did get a Balrog mesh from Lich Fathers or something like that which is really good, but I don't have any permissions to use that yet, I have to track that guy down.