couldn’t find any good skybox textures for free online… so I figured I’d ask you guys 
Post them here!
Don’t forget about the files M@dcow posted before in the sticky:
http://blenderartists.org/forum/showthread.php?t=24038&highlight=skybox
If you guys use 4096x1024 textures you will bring the game engine to a screaming halt.
in the game engine try to keep the textures square, or it will improvise and make a temporarie texture (in this case it would make a 4096x4096… this is not good…)
try using smaller seamless textures instead.
Check this link if you need any HDRI lighting. Even if you don’t, you can still convert the images for more basic use.
EDIT: Didn’t realize this was in the GE forum (clicked ‘New Posts’), so the above link doesn’t really apply. :o
Still . . . it’s a useful resource for other non-GE projects.
.