My view is to get members in the "field" and take new photos to make new photos. Field could be your table depending on what the challenge is.
To me it is a learning experience not searching your photo library to locate a photo(s) that meet the challenge.
Yes I recently "dumpster diving" to meet a challenge. Although I learned that it reminded natural framing of a subject is a powerful composition technique. Usually, for me, it's a serendipity experience.
What is your view?