Hehe, I can understand that frustration! Ironically enough, I tend to go off my own interpretation of the characters, in terms of body shapes/structures and all. However, must say that it’s all pretty inspired by Kayla Na. 

http://pingagirl.tumblr.com/search/FNAF

I generally go the route of a skinnier Chica and Foxy, somewhat skinny, perhaps average size Bonnie, and big, roundish Freddy! 

Another picture I actually love to look back to on occasion is one may by Gheistly fairly recently! -

(Can originally be found here, for dA source at least~)

These aren’t the heights I myself go by for the FNAF crew, but these may also help given an idea of how to portray them in terms of full body. (I do find Chica in her more ‘actual’ size, if not a bit chubbier, to be just as adorable.) :)

But I started off by referencing a lot of other artists’ works with these guys before I pretty much wing ‘em now!