I know for certain ( I think... xD )
that his tattoos are Runes. More specifically, Norse Runes supposedly a gift to humankind by Odin himself. They're used as an alphabet but also serve as a system used for majic and divination. I assume that They either tell a story or they are a spell of some sort that he can use? Just my thoughts, really. Unless you mean the fish, in which..The great flood!? LOLOLOL!
But I love your comic very much. You make me a very happy fan with your updates~
Curious... this may be a shot in the dark, but some of his arm tattoo's look as though they are written in Anglo-Saxon Runes... in fact, I'm almost positive that's what they are, because I studied how to write the runes and make fancy schmancy sentences.
So... I'm going to guess the runes are there as either a seal of some kind, or a sort of short-cut for some kind of magic. The symbals could also represent words, for example: The "X" can be interpreted as the letter G or the word "Gift". The pointy "B" can be the letter B, or "Birch". The slanted downwards "F" at the bottom of his left arm, can mean "Ash" or represent the combined letter form of "ae".
But now I'm just rambling. x3
Though I believe Magical.Android.Aria had the right idea~
That one part of the tattoo on his right arm looks like a cross.
So if he had his arm like... held down by his side it'd make a cross the right-side up when really an anti-christ cross is upside down?
Really like the update though, especially the perspective in the last pannel <3