Mary Janes

I am sure that many of you have not heard of Buster Brown shoes or Mary Janes.  But in the 50s and 60s this was a big brand and every little girl had or wanted a pair of Mary Janes.  Leslie Saeta did some kids shoes in the January 30 paintings in 30 days challenge in January.  These are my rendition and I thought these would make a cute shower gift.  I still have several more that I want to do, but am trying to figure out the size.

My dilema is this, I started out at 5"x 5", see above, but found it difficult to come up with frames. 

Then I found the cute wooden frames, at my price $4.97 (yes I am cheap) at Walmart, lightweight wood that I painted my way, and had to go down to an image size of 3"x3".  Someone else had the opinion they should be 8"x10", but that is almost larger than life.  So what is the right size for these "pint size pics"?  Or anyone have some great ideas on where you can find reasonable frames in lots of sizes?   If 5"x5" or 7"x7" is custom then I have to go to standard sizes even though I really like the square format.

For the 5"x5"s, the black shoes are done in color pencil, and the ones on the right are done with acrylic and glitter on top.  In the frames - all of these are acrylic, with the background done with palette knife.  Oh yes, the nursery is done in lavenders and grays, so I put the pop of red on the outside and inside of the frame to pick up the pinks and fuchsias that are on each shoe somewhere.