It sounds like you are pathologizing your own creativity a little bit. Strange, whimsical, surreal ideas or unrealistic fantasies aren't necessarily symptoms of a disorder. The stuff you mention does not strike me as delusional or grandiose or overtly bizarre at all (especially since you are a writer) - this is what the imagination is for. Now, if you are having so many thoughts you can't even keep track of or remember them, or if you are calling galleries and publishers to tell them that you have the best idea in the universe and will make them a fortune with your creative genius, that would be another story...

I'm not saying you are/aren't experiencing a manic or hypomanic episode, just that from what you describe I would not be alarmed at the content of your thoughts.