It sounds like you have very creative ideas and I would strongly suggest not selling yourself short. When I'm having trouble coming up with an idea, I simply paint or draw subject matter that inspires me. Usually it gets the creative juices flowing and gives me ideas for other pieces I wish to create!
Perhaps I said that wrong, but what I mean is that I struggle doing it on demand. I am not selling myself short and I do make recommendations when I can, I just think of things randomly rather than when I want to.(Heck, some of the best ideas I have just popped up in the middle of a shower. No joking.)