What exactly are you trying to do?
Are you trying to make a skycube with blocks or are you trying to make a skydome with a model. They have completly different methods of texturing.

For a skydome you need an image with two parts. one half is tiled as the basic sky and the other is tiled as moveing clouds.

For a skybox you need an image that is made up of six different images... one for each side of the cube. They must be in the proper order and they must tile in a certain way.

There are some free tutorials in the resources section and read the manual to find out the proper image formats. The tutorials are old but the processes for making sky boxes really has not changed.

If you are still haveing problems post again and ask questions.

"Create a cube that is bigger than your level/stage/map (it doesn't HAVE to be hollow)" The skybox does not have to be hollow? Never heard that one before!