Its easy... Go in some kind of photo editor, put some white dots around it, clean em up a little, and make enough textures to texture the inside of a box. Go into the editor, paste those on the walls, fit em, and then set the 3d skybox thing. Even making just one texture that goes over all walls can work too. People just look up and go, "oh, its space"... They dont check all sides to make sure that every direction looks like the same set of stars.