See, this is what kills me with pixel art. Just when I've finished a full week with several hours a day working on a image the size of my toe, and I click
save with my sweaty hand, trembling with a caffeine overdose, someone like you comes along and says something like "Keep it up!" or "Oh, this is headed in the right direction. I'm looking forward to seeing the finished version."

But thanks! I absolutely agree with you in regards to the use of colours, but I only had 18 colours to work with for the challenge. If I had more colours, I would try to experiment with that. I could try to juggle the colours around to free up a couple more colours, but... I'm going to stop here, before I go postal.
After deciding to go with a pink-green palette, I actually did start out thinking that this may be a bronze statue, so your impression of the mask is quite accurate, in that regard.

Final version here:

Thanks a lot to everyone who helped me. I need some more coffee. And maybe I'll start smoking.