@Remnic: Those look more like moons to me... unless the Mushroom World has more than 1 moon then it's ok... although I doubt it... And it needs some actual stars. ExAnimation, perhaps?
Good ol' Yold Desert .. nice work. There's two things that I would recommend though:
-The leaves on the tree look off. They look like they don't even fit on that tree. You might want to tweak them a bit.
-There is a long white line between the rock and the bush on the ground, giving the illusion that they are "floating. You might want to fix this too.
Good work - it would be interesting to see what kind of unique areas you could make with this.