Alrighty, now that we all know what patina IS, let's talk about how to fake it. In my case, I have been collecting assorted frames of all shapes, colors, ages, and sizes for the past six months, with the intention of creating an epic "instant" antique map collection to hang in my upstairs hallway at the farmhouse. Once I'd gathered a decent stack of frames (sometime around September of 2014), I laid them all out in my yard, spray painted them all gold, and then got too busy to finish this project. (I know. I'm the worst. But I was going to France for four months, so there was a lot in the works. Get off my back!) Anyway, fast forward four months, and I'm finally revisiting this project.
(Though actually, almost everything in my house is already third or fourth hand and usually very used, so there isn't much that doesn't already have an authentic patina on it...)