I used 17 blocks and printed 15 pictures, so bearing in mind that I needed 8 spaces on the front for my letters to spell "scranton", I put some of the pictures on the sides as well. Do a test on your photos with the mod podge, because depending on the type of photo paper, the ink may smear (mine did, so I only applied MP to the edges and the back, not on top of the photo). After the paper and the pictures are dry, you can apply your letters. I used clear rubber stamps (similar) and purple ink (I didn't love the type I used, this is better), but you can use rub ons or stickers as well.
After all of the blocks are finished, you can either leave them as they are and stack them up somewhere they won't get knocked, but I am constantly moving things around, so I like to glue my blocks together with yet another layer of Mod Podge. After that last layer dries, you're all finished! I put mine on one of my book shelves and hung my graduation tassel off of the top for a little nostalgic touch.