The dithering on top of the sk is too uniform... doesn't look too good... Also I'd use some antialising on the border of the right mountain.

 wow just 4 colors. good job.

Nicely done.

thanks, I added a little more contrast :D

nice rockz, yeh i agree, a little more contrast might be better.

I like it

Cool, nice feeling. However, I'd suggest changing the fade of the sky- the regularity of it contrasts too much with the rocks below.

 Looks nice, but the low contrast makes it hard to read.