I've made 30 space skyboxes for my space game, which can be of use to mappers.
The image files are 1024x1024 PNG quake3 style environments and were made with Alex Peterson's Spacescape.
The source XML files are included, you can use them to render higher resolution versions or create your own.
Space skyboxes means there are only stars and nebulae, no mountains or other scenery.
You can use them as-is, or use them as a base and merge them with your own landscapes.
I also wrote a Spacescape tutorial which could help you to create your own space vistas.
Note: to convert Spacescape output to quake3 you need to swap left and right images,
rotate the up image 90 degrees and rotate the down image -90 degrees.
