This is actually a 'real' collection in the sense that I've gone out looking for very specific postcards to add to it and have invested time and (a small amount of) money in it.
They are postcards on a seaside theme, carefully chosen with art projects in mind, so a lot of them have people in the foreground:
I especially love these washed out looking ones with many people wandering around:
Ooh, makes me want to head for the edge of the land... Here are a couple of my (big -- A1-size) pictures based on postcards: