Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Easy to Use Platformer Set Free.
Easy to Use Platformer Set v1.2
Easy to Use Platformer Set v1.1
Package containing pixel art
Ideal for simple yet cool platformer game.
-20 tles
-3 trees
-sky
You can build basically any platform game level using this asset. Trees are bigger than tiles,and in single separate files, so it will be easy to use them for paralax effect, or randomly generated 2nd plan.