It was requested a few times to have a map of Aziraphale's tattoos! I think the halo in the crook of his arm was probably the first one -- maybe associated with some sort of medical thing where he had to have blood drawn frequently, like my sister when she was a kid. Then after that he just got really attached to magnolias. To me they represent a place that feels like heaven on earth.
I thought about putting him in his birthday suit, but I don't think we're at that point in the relationship yet. I wonder what Crowley will say when he finally gets to see all those flowers, and realizes they match?