Here's some examples of commission type vs prices for the ones I commonly do, so that you can get a better sense of what price I might charge for your project.
If you're not sure how large and complex you'd like your work to be, I'd be happy to do brainstorm sketching first for a flat fee, to help you explore different ways your artwork can go. The final complexity and price can then be decided depending on which one you pick. Please feel free to ask me for more info on your specific ideas!