Download a new app called Stack Collage available on either Android or iOS. Among many uses of being a great tool to import photos and draw on them, you can add multiple photos into a photo stack and create super fun collages. In addition to this, Sports Dood coaches may want to load in a bunch of plays and quickly pinch zoom into a particular play and overlay some doodles in a quick demonstration of a play. Below is a quick screen grab showing how you can move images around via multitouch and really provide a quick and easy flexible surface of images.
Try it out, it is free