A good place to hang an empty frame collage is the wall along a staircase. You can find all the old frames that match this idea, then delete the photos and windows that are there.
You can see on the picture above how, again, the name of the game is contrast. The style gets its appeal by focusing on different frame sizes. You can also place smaller frames in larger frames to play with geometry. Different styles in the frames, from the most worn to the metallic, could also contribute to add visual interest to the display. You can play with different frame widths to add more contrast. Also, feel free to play with different frame colors.