Hi,
May I first say you've done nice job, especially as Santa said, in breaking away from the standard green! It's a really nice and welcome change from the horribly garish green Orcs normally are.
With regards to the wings I'm not sure whether I agree with Count Lasombra's idea of doing the membrane purple. The could certainly use a little more to differentiate them from the rest of the model. In my opinion membrane needs to be worked from the same palette as skin keeping the tones similar, but making it much paler. Maybe try mixing something like a tiny amount of Elf Flesh and Dheneb Stone/Bleached Bone in progressive amounts to your to make it the little bit paler. After all, if you look at the little membrane between your thumb/fingers it's the same skin, just thinner.
I also think the face could do with a little work to make it seem more living. At the minute it seems quite cold and lifeless so perhaps you could try red and purple washes in the facial recesses, paying particular attention to the eye and nose areas. Red and blue naturally go together so it could look quite nice.
Other than that, you should be really proud of a cracking paint job. I can't wait to see the finished product with the rider on top.
Happy painting,
untitled_musketeer