That looks quite good. However, there are a few things that don't quite work for me, mostly due to the dithering.
-The head is really blended into the shoulder area; I can't tell where the snout ends and the torso begins, even when zoomed.
-The X's on his front leg look quite strange; try other dither patterns instead, as per Helm's suggestion.
-Maybe you aren't done with it yet, but his right (our left) bicep, shoulder, and pectoral areas look very flat and a bit strange musculature-wise.
-The forehead is also a bit flat, but not nearly as bad as the abovementioned parts.
-Tiny nitpick, but what's that random block of four light pixels in the top-left corner?
-It's probably a bit too late to change this, but somewhere in the flurry of edits the pose changed from a very dynamic one to a more brooding, forboding one. The current pose fits the color scheme, but the original pose was a bit more interesting.
Good luck with the contest!
