uuh ya... But when u make the sky dont make a big sky box around your map.. It will just increase lag.... alot. Just put the sky bow where u need it so it touches a solid map object and there are no openings to the outside. You can see what skys you already have by going to
in there you will find lots of .tga files.. example
That sky is called "backalley" dont take the last 2 letters.. those just represent where that part of the sky will be placed.