I think the biggest thing that sticks out right now is how dull everything looks. Although it could just be my laptop screen, I'm going to have to say that saturation is your friend right now. I mean, it's great that you have a unified palette, now your next step is pushing the palette to it's limits.
It's been a few months since I properly pixelled anything, but from memory, I think you could achieve a metallic look and cloth look with the same colors; it's just based on what colors you place them next to. A metallic surface is going to be shiny (I'm assuming), so if you're using a saturated green, for example, use white for the highlights, and for the cloth surface, use a duller color for highlights, if any at all. I donno if that makes sense or anything...hopefully you get something from that.
Keep pixelling.