very cool model, really liking this creature - kind of an anthropomorphic gargoyle.
As alluded to previously - the wings kind of stand out. Google image search "Wingsuit" to see how the structure would look if its purpose was flight/glide assist.
Not sure how much you are willing to deviate from the concept, (concept art would also be cool to see if possible) but unless you're going for a vestigial style I don't think that flap coming from the bicep to the pecs would really do anything but create drag. It would seem more practical if it went up more into the neck.
I know its a WIP but the level of detail on the wings doesnt seem to match the rest of the model. It could use some veins and small bones in the same style as a bat wing because just a flap of flesh presumably wouldn't hold its rigidity.
It might have been beneficial as far as the wing structures are concerned to model this guy in a T pose although it may be a bit late at this point.
Watching this thread with bated breath regardless, great work!