Well I don't know exactly, since 2 cases can be made for it (both for and against) but I feel if you're gonna do it, you should at least ask.
I'm a new member but a fellow fan base member said he liked mine a lot and would want to use it. I took that as a compliment and few days later I changed it, and he used that. IMO that's the best way to do it
Sure it's just a .gif file on an open forum but a little courtesy never hurts.