Infinite Picture Menu?

Can anyone help me with this. I am trying to make a infinite menu of thumbnails called dynamically. I need two things: I need the menu to move forward (infinitly and at a constant rate ex: speed = 5) while the user presses and holds the forward button and backwards (infinitly and at a constant rate ex: speed = 5) while the user presses and holds the backwards button. Secondly, I need randomly sized pictures (ex. 640 x 480) to load in there respective box (20 in all, each with a varible P*(number)*) and be scaled to the size of the box with the pictures proportions intact. Attached is what i’ve come up with so far and i’ve used the pic box currently in the middle of the project to experiment with.

Thanks in Advance =)