I have a large mirror in the hall which up until now was framed by a long, artificial, hanging ivy. The artificial plant (not a natural one because it's very dark in the hall) has now got dusty and unsightly and I have had the idea of replacing it with a frame of cork tiles, to which I would pin random photos and post cards.
(In fact, the ones at the bottom I would have to stick on because the toddler grandchildren could pull out the pins...)
The cork-tile-frame I had thought I would make by cutting the tiles into smaller squares and arranging them at different angles to make a sort of crazy-paving style. Similarly, the photos would be pinned on at varying angles and overlapping - so there would be room for plenty.
The mirror seems to be in place of a door that may once have been there, so it is set back from the wall. The basis for the frame could be cut out of MDF and screwed to the wall surrounding the mirror.
You could do this on any spare piece of wall - hall, landing, stairwell or loo. The basic shape needn't be rectangular.
So that would be a large-scale project which would use up photos. You can change them about as and when you get new ones or fed up with some of the old ones, or you can stick them down and varnish over them. But do scan them first. And note down who's on them. You never know when you're going to start forgetting!