There is no set limit on the number of pictures you can use.  We do ask that you have enough pictures to fill at least one song, which would be between 25 to 40 pictures.

The general guidline for pictures is 35 to 45 pictures per song, unless your song choice is very long (say 4 1/2 to 5 1/2 minutes) then you may need 55 to 65 pictures for a song of that length.