First of all, I'm going to put these out here BEFORE I try to write a category. I see folks in the forums getting their feelings hurt or being angry because they got a negative vote, but they never put their ideas to the "membership" to get ideas and work out bugs. I've never tried to write my own category, so be kind...LOL! 
That said, how about a
1. "Women in History" or "Famous Women"" category? There is a category for statues of famous people, none of them women. It could include statues, plaques and memorials of Women worldwide and also those hometown heros who leave their indellable mark on their communities.
2. A waymarking game to mark and record the "Colors" of Motorcycle Clubs around the world? My big thing with this one is how to prevent duplicates? Instead of an other waymarks in the area posted flag is there an option for "sounds like" flag?
3. Artificial Reefs and Reef balls. I ran across one on display at a local shopping venue. It was really neat, but I have no idea where you might waymark such a display. If they were underwater, there would have to be documentation by way of a chart picture identifying the reef or if they are near a pier, a sign stating that there are reef balls under the pier. I think most piers post such things....ours here do.