Space CTF's skybox is in pak16 at \textures\skies\env
Code:
To replace them you'd have to cut up the overall image that you've found into the 6 that are in there (It'll involve some effort)
Unless the image you have can be stretched without looking REALLY weird, then this won't work
You'd have to download a skybox (You can get some here) or you would need to make 6 separate images. (It has to be like a box to work)

Originally Posted by
Wolfcam thread that's no longer visible
For moviemakers who either don't like the current skies, or have something special that they would like to replace the skies on all the maps, there is a "skykey" cvar out now (as of v7.2). Use r_fastsky andr_fastskycolor to chroma key the sky, and use r_forcesky to force the sky to a specific shader.
Example:

Originally Posted by
brugal
seta r_forceSky textures/skies/hellsky