You've submitted a lot of really good artwork but I wonder if these would benefit perhaps from a bit more contrast? The actual pixel work itself is great but there's very little contrast between the different shades.

For example, a very quick tweak in PhotoShop (not suggesting they necessarily use these exact colors):

This makes it easier to see the details.

Of course I'm somewhat colorblind to certain shades of red and green -- RedShrike could offer some good tips I think on color contrast.