Is it normal to send friends pictures of yourself as the opposite sex?

I'm a guy. Sometimes I cross dress for fun and take pictures. And then I send my friends those pictures (no face) and make them think it's some chick I found on the interwebz. The pictures I take are pretty convincing so they fall for it every time and never know it's actually me. Some have told me that they've gotten off to those pictures. I'm not gay, but it feels good to always get a great response. It's also hilarious, but a pretty harmless prank. Even if I told them it was me, they would not believe me. Is this normal.