did you resize the picture or something? because something is off with your shades, you created a bunch of new unnecessary ones in what ever process you did.
For example the stone pixelart on your deviantart is totally fine too in the big piece, but the two smaller ones above have the same issue with random pixels. I'm talking about this one
http://leocirius.deviantart.com/art/Pixelart-Ej-0003-451260336
I can only explain this by the fact that you somehow resized/saved as jpg and than resaved as png and thus created those weird shades.
Hope you can figure it out and fix it since I really enjoy the piece.
Composition and such looks pretty good ('though you have some jaggies, most of the noticable ones in the big text), but you're using far more (near-identical) colours than is needed. You've got 87 different colours here when you need only maybe 8-10 at most and possibly as few as 6.
oh, I understand, thanks for the feedback :)