I want to write a book...?

I dont really have a concrete idea. Ive always been interested in writing and I want to actually compose a book and have it published. I care nothing about making money off it, I just want to write it. I have a few ideas but Im looking for something more to expand off of. I know where to go once I have an idea, I dont need people telling me to brainstorm, I have some ideas, I just want an outside opinion that I can run with.. anything will help, I can run with a small idea or add onto a larger idea.