Some of the photos sent in are "arty", but many are just a record of ordinary life. Looking back over the years, you can see what you were doing.
Often the most mundane subject matter is popular. Some years ago I remember a photo of mine of a mole hole being widely viewed, whereas something I thought would interest many turned out not to be.
We mainly do this for a record of what we did rather than to be particularly popular. It is great fun. The secret is not to take things too seriously.