I have been meaning to do this for the last few weeks. Yesterday, I finally did. I stopper by Wal Mart and picked up a frameless 20 X 30 Poster Frame. Its a sheet of acrylic that uses snaps to lock it in place. Smaller versions use a glass sheet. I use them for everything. They are very cheap.
So I flipped the cover sheet over and made a template. Then
I cut out shapes that were roughly the same shape as the bubbles on the
Micronaut Alien cards. I put the Carded Aliens over the template, put
the freshly cut acrylic sheet over and now they are ready to hang. The
cut outs also help to keep the cards from moving.