My wife commissioned me to create/find some way to frame the small canvases she painted as Christmas gifts for her family. It seemed like a fun project, so I set about adapting one of the many great frames here on Thingiverse.
This frame is for holding those small 2.5inch hobby canvases you can find at Michael's or Hobby Lobby.
You can really use any print settings you want to get the desired resolution, however I recommend printing it vertically, upside down, with supports only on the back lip. (See picture for what I mean)
Assemble it like the picture. A 2.5inch square canvas should slide right in if your printer's dimensions are correct.
Found a decent frame and edited it with OpenSCAD.