So I did.
While I was at the market, I came upon a vendor with these trim pieces off of old houses. I'm not sure what they're called, cornice boards? Then when I went past the vendor they call Doorknob Bob, I bought a few old doorknobs from him. I washed everything real good and got Tom to cut the knob stems in half. Then I marked where I wanted each doorknob and drilled holes the size of the stems. Because the stems are square and the holes I drilled were round, the stems wedged in there pretty tight. I think they're tight enough so that they won't get pulled out, but if they do, I'll go back and glue them in.
Hung up in the barn apartment, ready to hang things on.
Next up...this fireplace surround/mantel that I bought a couple of months ago. I've painted it black and as soon as I find some suitable fabric, I'll make it into a padded headboard for one of the guestrooms in the house.