What's kind of the problem, it doesn't look finished - lines are still pretty loose and that's especially noticable because the sky (is that the clouds filter in PS?) is filled witzh sharp edges. If it's supposed to be a sunset of 2 suns, shadows should be sharper like at the bottom of the hills and such.
There's also a lack of details in the foreground, or to be more precise they're about the same as on the background.
And the perspective of the cliff is a bit off, especially if you want to scale a sprite on it.
Also the 2 hills in the back sort of seem to repeat.
On a personal note, I don't really like this types of background, almost always the sprites look unnatural and glued on.