And then I saw this cool wine cork bath mat and felt inspired.
Here's the how-to.
Gather your corks, a really sharp, non-serrated knife and a self-healing cutting mat.
Be very careful not to cut yourself while cutting your corks in half, lengthwise.
Arrange them however you like on the back board of your photo frame.
You can be way more simple than I was, but I wanted something more than straight up and down or side to side lines, personally. Of course, this required me to cut the corks into a lot of different sizes...
After they're laid out, use your glue gun to glue them firmly in place, one and a time.
I found it easiest to work my way around the edges and then press the middle ones tightly into place.