While it isn't so much a prompt, something that helps me re: my creative endeavours I'd like to do more is just saying that each day I will do 5 minutes of it. I can do more, but I only have to do 5 minutes to count the day as a success. Usually I end up getting involved and doing far more than 5 minutes, but on days I'm really not feeling it I can do that 5 minutes and know I did my chunk for the day. I think it can be a good way to get yourself motivated when you have the Brain Worms (I don't have adhd but I have my own selection of activity-halting-issues).
As for prompts...do you have any OCs? I always just want to write my characters in different situations, think about the conversations they'd have, how they'd respond to something, etc.