a tutorial how to make your own moving sky textures is described in the linked thread
As I mentioned above, that thread has the same topic and has some other variations.
What you need are seamless
Just like the ones for world textures for example (or static skybox).
Textures are placed like a mosaic and MUST therefore be seamless:
Left side matches right side and upper side matches lower side.
There are existing software that can help you with it.