Now if you've read my blog you've seen me use iron wall art and old mirror frames as ceiling medallions, but by far the cheapest solution I have is old plastic lids.
Basically I found an old bucket lid laying on the ground outside my house (someone's trash most likely), and when I picked it up I thought, "that looks just like a ceiling medallion." It was too beat up to use, so I decided to see what I had around the house.
I looked in my tupperware drawer. I put all the pieces together to see what was left. I had a couple old larger plastic lids that didn't fit anything left, so I painted them, and put one under my bedroom ceiling fan. You just need to cut a hole in the middle of it to make room for the wiring, etc. (just like a real medallion has).
I put the other under my bathroom chandelier.
Easy FREE solution to something I would buy anyway (I for some reason just can't stand the look of a little 4" cap on a big light fixture). I would have preferred larger bucket sized lids, but I used what I had. In the future I'll be hitting up construction sites for more, when I ready to add them to my daughters rooms : ) Happy hunting.