In this case, there are never too many topics, you can expand the range, I'm sure that people have something to share.
I agree, there is already a flower contest in another community, but we can have a flower contest in ice, or flowers floating in water, lol. There are many items under our feet that could be the subject of an interesting contest, like fallen tree fruit, rotten fruit, trash, fallen leaves, whatever. the competition of shadow photographs cannot be called exclusive and the competition of reflections, but even here you can think of something, give each competition a narrower topic, for example, the shadow of a mosquito proboscis :).