Much, indeed 🙂
Anyway, go crazy in this pack, just have a look at the source material (since you used a cat as an example) 😉 :
http://s47.photobucket.com/user/01978/media/bd83624b433922338528ffb9a38ddc2d4ec.jpg.html
Feline muscles tend to be very impressive, one domain where bigger is probably better, hey 😉 😛
Plus they work fine (recolored) for demons, devils, imps, etc… 🙂
Oh, and yes, I think the main bulk of the character matters a lot. In my opinion, unless you’re trying to draw a fairy (but well, then you should use one of the elven packs shouldn’t you ?), the guy should be big and impressive enough so that meeting him in a dark alley doesn’t sound like a good idea… Even if his look is somewhat exagerated…
While dealing with supernaturals, I believe we left human proportions and rules behind us, didn’t we ? 🙂