To change the image for P7 skydome, enter the material room and click on image_source on the Color_Texture node (depicted as 1 in the image above).  That will open the Texture Manager panel, click browse (depicted by 2) navigate to the skydome texture folder to select a new image.  The path for the skydome textures is *Textures*>*Modualz>Sky.

*BTW, IIRC, there is no way to rotate the skydome automatically for animation.