Experimenting with small prints laminated together and placed in my cell phone case. I have 9 in the photo but can probably fit at least 15 of that size with no stacking or overlap.
Edit: In windows you can select multiple photos and print them together on the same sheet of paper. Just select the photos and right click to select print from the dropdown menu. You have several choices such as up to 9 wallet size or 35 contact print size photos on 1 sheet of paper. In the screenshot below I selected 11 different photos with 3 copies each of contact print size for a total of 33 prints. For the ones I put in my phone case I also reduced the size of the photos to 50% of normal in my printer software dialogue.
