Protecting Your Trademarks on Facebook
To select your username, go to this Facebook link. To learn more about the Facebook usernames, visit the Facebook Help Center.
Further, if you have a registered trademark for your photography business, you definitely should consider acquiring the corresponding vanity URL (check the blog for more info) or making a filing with Facebook to prevent another party from acquiring a vanity URL with your trademark. The Facebook system only permits owners of registered trademarks to prevent another party from establishing a vanity URL with that registered trademark (so unregistered trademarks cannot be used for this purpose).