Edit: Vertically cropped image, removed second image, mostly placeholder art.
So, specifically, I am working on the backdrop right now.
I'm working on a platformer\rpg, starting to try to clean up the tileset and add a background to the first level. The only thing in this that I did not draw is the main character sprite, a guy on the SomethingAwful forums drew it for me a while back.
So, I'm drawing assets to the best of my capability, I feel like I'm getting better and maybe someday it will evolve beyond "programmer art"
For this, I do want to keep a boxy, simple, relatively flat look, realistically that's the extent of my ability and it would look worse if I tried to overwork it to make it look better.
I'm stuck on outlining. The first screenshot, should I outline all the trees, and both layers of background foliage?
I'm leaning towards yes, outlining the trees, but the trees in the second row outline with warmer, less contrasty color. The foliage nor background ground I can't decide.
Is there any rule of thumb that should be applied here? I don't want the background to be distracting, at all, but I also don't want for it to look washed out or like I'm afraid of contrast or saturation, because that look is no good either.