Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Platformer Maps Free.
Platformer Maps v1.0
3 types of maps for platformer games. Such as desert, forest and winter landscape. All elements are in PNG format. Also you can find the example of a map in PSD format. In addition asset includes bonus art (box, barrow, wooden parts etc.). All art are in a high pixel size.