I make my mug rugs 5x7 inches. I bought cellopane recloseable bags that they fit into. Shop around and your can find some really nice ones inexpensively. I print the little info paragraph on some decorative paper and slide it into the bag on the back side of the mug rug. That way, they stay "sanitary" and people who give/receive them know what they are. They are pretty common to us, but the general public needs the explanation! I also printed out on some bright paper what they are used for and set it by the display. People commonly ask me, "What do you do with them?" I point out the paragraph and my list of uses...office gifts, something to give with a birthday card, an acknowledgement of a kindness, hostess gifts, etc
I sell them by the hand full at craft shows that I sell at. However, I do not quilt mine. I use machine embroidery and they are all done in the hoop. I have found that people did not buy Christmas ones no matter how gorgeous they were. Last year I did not sell any Christmas ones. What sells for me in my market are ones that have a theme to them and something that makes them laugh. I think that coming up with thematic ones would be easy, but the "funny" part more difficult. Also, you'd have to buy thematic fabric if you don't have any...like jungle, flowers, coffee, etc. so you'd end up using a little bit of a lot of different fabrics which can be an expensive initial investment.