Printer + cardstock
Paper cutter + corner punch or scissors
Clear iPhone case
I printed out a page full of images to not waste paper - then I can switch them out when I feel like it.
The size I made each image was 6 cm x 11.5 cm. This creates a tight insert which leaves room for trimming within the photo a bit. Most clear cases come with a cardboard insert that you can use to trace as a template, but if you are like me and happened to already have a clear case and have just come across this idea, then you'll no longer have that handy template! I've scanned my template and have it here, if you'd like to print it off or use as a digital template:
Cut out each image and use corner punch to round the corners (or use scissors if you are patient).
I used a hole punch to make the holes for the camera and flash as I thought it would be quicker and cleaner then trying to cut out a nice oval to match the case.
You could also use scrapbooking paper, here I had some digital scrapbook paper and then printed it on cardstock. I think cardstock will hold up a little better.