i like the top of the plant and the grass, but the leaves on the plant and the stem have no detail. im sure you're going to add that, but just someting i noticed. theres also a few spots in the grass where its flat, as apposed the the rest of the grass sticking up.

also, the line art on the rat looks off for some reason. the area behind the wiskers is very pointed for some reason, and just looks a lil off to me.

other than that, its lookin good. Cant wait to see the finished version.

I dunno if you're shading it that way on purpose, but it looks very flat. More shading across the whole thing would look better, I think:

(This is obviously not pixelled, but it's less of a cheat than you might think -- just two semi-transparent layers, both solid blue-gray. You could probably achieve a similar effect with the selective use of a color-replace brush.)