We were at the candy store, I mean Home Depot, the other day. We found a bit of wood in the hobby aisle, and thought to make a picture frame. We found a piece of plexiglass 8x10 in the glazing aisle and we were on our way.
We came home and mitred the corners using a hand saw and the mitre box, then glued them together with wood glue and held the wood glue in place while it dried with painter's tape.
This is where our design could use some help. We pre-drilled holes in the plexiglass so it wouldn't shatter, and screwed through the glass and frame to attach it. You could do two sheets of plexiglass and slide a photo between.
On the back, we mounted picture mounting hardware and my son wrote his name.