Get a large sheet of paper in a dark blue or black. If you can't find a huge sheet like mine, use poster board or several sheets of regular size paper. The exact size doesn't matter, just get it however big you'd like. I used masking tape to secure it to the wall I wanted to decorate.
Use white acrylic paint to add stars to the top of the paper. You can go for the regular star shape or the more abstract version like me. Think: fuzzy circles. Bonus points for including constellations.
Paint your landscape. Triangles for mountains, with a couple of sukkahs in the middle for me. You can add trees, a river, city skyline or whatever else you want.
When your paint is dry tape leaves around the top to represent a sukkah. I used ferns from my yard.
There you have it. A simple piece of Sukkot decor you can easily make yourself for little or no cost.
Chag Sameach Sukkot!