OpenRA

I was thinking, is it possible to create your own, new theatre set?...Like, add a Lunar, Urban, desert set for OpenRA, besides Temperate and Snow.

Yes, it is possible. We have a tool (TilesetBuilder) in the git repository which allows you to import a bmp of tile artwork, and export a tileset. It is currently incomplete (specifying terrain types doesn't work properly, and the details are hardcoded for our d2k arrakis tileset), but the output it generates is enough to get the tileset working ingame.

Okay, late response...

I downloaded all the files from the git, yet...they are all files I don't know how to open.

Seems I have to do a file and run it or...I don't know, what should I do?