Ok i tried this on PS7 and PS:CS
so iam not sure if i will work on older versions.
Ok lets start off
A good place to find a video clip is here http://gametrailers.com/
so get ur trailer in MOV format and go ahead and fire up ur image ready
now open the file and this screen should pop up
you should select "selcted range only" and chek the box for limit to every frame 2-3 will work fine. now hold down ur shift key and drag the movie pointer thingy for the part u want and click ok the part you selected will apear as a gif file with so many frames+layers. now try to keep the file relatively small about 8-10 sec will do fine for now(dont be mean to the 56kers)
now get youre background/sig and get the sizes of it... and change the canvas size of the video file to fit the size of ur background. now move youre background into the video file and put it below all the other layers. now if you want to move it around a bit just clip all the video layers together and abjust it and i belive youre done. (dont forget to save it in gif)
note that thi is my first tutorial so bare with me for any mistakes i made
