Firstly you will need a piece of software from AMD called "CubeMapGen".
You need to get the version direct from their website here:
http://developer.amd.com/resources/archive/archived-tools/gpu-tools-archive/cubemapgen/

If you installed it to somewhere other than "C:\Program Files (x86)\ATI Research Inc\" then do this bit.
Locate wherever it is and copy the path.
Now edit the file "make_cube_map.bat" in this folder and change the line
"C:\Program Files (x86)\ATI Research Inc\CubeMapGen v1.1\CubeMapGen.exe"
to the actual path to the program "CubeMapGen.exe".

Cube map face mappings:
cube_face_0 =  X right
cube_face_1 = -X left
cube_face_2 =  Y up
cube_face_3 = -Y down
cube_face_4 =  Z ahead (forward)
cube_face_5 = -Z behind (backwards)

TO bake the images into a cube map just run the batch file.
TO see them in Pioneer you can treat them like any other mod.
Put the default.dds into a path like "/textures/cube/default.dds" and zip it up, then put that zip file into your "/documents/Pioneer/mods/" folder and it should automatically use it.

Alternatively you can create a series of files called "ub#.dds" where the # is replaced by consecutive numbers.
Be aware that the numbers MUST be consecutive or you'll get a crash so "ub0.dds, ub1.dds, ub2.dds" is ok but "ub0.dds, ub1.dds, ub3.dds" is definitely not.

If you do this then Pioneer will pick from the selection you have provided when jumping into a star system, it's pseudo random and so will always give the same result of a specific system.

Enjoy.