I think of eBay as a street corner where everyone from all over the world is setting up a booth and selling stuff. Some is good, some is bad and a lot are so so. In art you get everything from serious artists looking to introduce themselves to new art lovers, to mass producers masquerading as artists to sell cheap art. You name it, eBay has it.
These tiny gems are no less art because of their size. Well framed with generous mats, they can be very impressive. I would suggest a 2'” white mat all around, and a simple frame to bring out the art. You could go more dramatic as well and put them in wider mats. That would actually pull the viewer in if the artwork is compelling.
Anyway, I have a few nice watercolor ACEOs there now. I hope you will take a look!