Brainstorming is the key word. It means to sit down and let your mind put
out every conceivable (also crazy!) ideas around one set theme.
I started to use this many years ago for other purposes than stock photography, and it still works fine.
In a session, better still if with another person or two, you can come out with many ideas, from the most 'common' to the most absurd. The trick is not to let our 'logical' brain discard the latter. Put them down on paper anyway.
When you'll start to select what is feasible, good and practical, you'll find sometimes that 'craziest' ideas, maybe with some twist and adjustment, can became actually very good ones!