I love antique frames. They have so much character. I have a wonderful old family portrait from the mid-1800's hanging in my home. It's of a distant aunt, Maggie Watt. Her painting is nice, but half of why I love it so much is the frame. Pieces of the gesso have chipped off. The frame is clearly original. Maggie just wouldn't look the same if I put her in a modern frame... even a pricey one that was really beautiful.
I am currently looking for a frame to serve as a message board in my kitchen. I want to paint the back with chalkboard paint. I have a great spot for it. I check every booth in every antique mall I go into.
Another great use for antique frames is to reframe modern art in them. You have to be careful with measurements and you don't want to cut some pieces of art, but with a French mat, one of these beauties could really live again.