Hey, cool Mini, the skull and the sheet are great.
Your silver NMM looks okey, on the Gold NMm you need some more brown, it looks ab bit too yellow. The darkest parts of Gold NMM can be pure black.
The base is a bit too bright for me, I think, because it takes the focus of the Mini itself, which is very dark.
Overall just some little points, which can help you a little bit maybe :)
regards HonourGuard