Once you receive your commission you can display it wherever you like, either on the web or as a print. You may print it for personal use as much as you like. As a courtesy (but not a requirement) I would appreciate if you would include a link to my blog when you display it online.
You must not edit the image without permission. You must not claim that someone other than myself made it. Unless we have a written agreement in place, you must not sell it, or prints of it. You must not use it to advertise other products that you plan to sell. You must not use it for profit.
By the same token, I must also agree not to sell the image or use it for profit. I will display it on my website or in my portfolio, unless you request otherwise.
If you want to use the image for profit, including posters and merchandise, contact me and we can draw up an agreement. This may incrue additional charges.