What is the background about the tattoo around Jellal's eye? Why does Jellal have the red tattoo around his eye? Where did it come from? Is there anything special about the shape of the markings?
Fun fact, this is actually a reference to Hiro Mashima's (the author of Fairy Tail) other series "Rave Master." In that show, there is a character named Seigrain, who has a tattoo over his eye, which is the same as Jellal's. This character also looks very similar to Jellal's.  

Sometimes Mashima sneaks in stuff from Rave Master. Such as Plue, who he describes as his own pet who he can use in whatever he likes. So, that's probably why Mashima put it in there.