This is awesome! Displacer beast are by far my favorite Creature of any setting and they come in all shapes but this one i just think nails it. And if you don't mind i'd like to just put forward a little request if possible could you upload a larger size version of the picture to be used as a wall paper by any chance? Id be forever grateful as would many other displacer enthusiast i'm sure.
I find it funny that in 3.5 this creature was very thin and had a very alien feel to him with some cat like features. As the editions have continued he has become more cat like and buff. I’m not saying that this is a bad thing, 4th had my favorite art for the displacer beast. I do feel however that the muscle n this particular beast is a bit much. It makes him look very powerful indeed but all that muscle detracts from the tentacles on his back. It also makes him look very solid. The displacer beast has its displacement ability which makes it seem as though it is somewhere it is not and I do not feel that having such a massive looking enemy gives it a feel of illusion. A slimmer form also flows better with the tentacles though the curves in the tail you drew also help. I do think you did a good job with drawing the muscles but I do not feel that they fit perfectly with this monster. The back leg in particular I find very nice, it has the muscle but not to the point that I think he is a body builder among his kind. I feel a little out of place commenting like this because you are far superior then I at drawing, the displacer beast is just one of my favorite beasties much to the agitation of my PCs.