Yeah, I use image codes for my posts, just because it's easier, and I was once told by a new member that he had seen pictures of something i had done and it was part of what prompted him to join.
So I guess my pics can be seen by guests, which I don't mind at all. If you don't want non members to see your customs, though, you should probably attach the pics instead.
Thanks for the link, Damo. I knew something had been mentioned about this before, I just couldn't remember where.