I've included the OpenSCAD source, plus the STL files for an 8x10 photo frame.
Print 2 of each side, 4 corners and a hanger. Layout the frame face-down. Center the photo on the frame. Pop the corners and hanger in place. Add tabs to any remaining holes if you feel like it.
It's designed to take a hanger on any side, so it can be hung vertically or horizontally.
The author marked this model as their own original creation.