Looking very rough (technically, not conceptually I mean). Ignoring the char sprite and foreground, I'd say all here is only the result of quickly blocking in your basic shapes. Good so far, but you haven't gotten very far yet.
Mountains are built up but then lean over, which won't ever happen in real life so it creates an unreal effect, yet overall just seems wonky to me. I do like the general right-pointing direction of the mountains, implying movement to the right - makes sense if your game scrolls to the right. Perhaps refining the bg will give it more credibility. The pink clouds are nondescript, make them poofier, more cloud-like, I don't really like how they're simultaneously in front of and behind the mts - doesn't make sense to my mind as I try to establish what depth/distance from camera everything is. If you wanted to parallax them separately you wouldn't be able to.
If you're going cell-shaded style, at least think about affording some AA colors in your palette. Non anti-aliased (or aliased) graphics always remind me of poorly rendered vector shapes - they bug me on a technical level. Though, they can be done in such a way that the desire for smoothing is minimized.
