I would improve only ground ( use dry pigments for example). Flanks of the base needs one more black layer. I dont like his camouflage on his face. Red colour is not the best idea to hide^^
Take a look at hind sight of that black one. I think area around that red gem need blackline.
Sorry for my English. I hope that you understood my notices. I really like this small diorama. You had great idea. Gratz!
Keep on painitng.