ballyharnon had an interesting discussion about what the runes on Sirius' mug shot might mean (http://www.livejournal.com/users/ballyharnon/73218.html)

Frankly, I'm going with my idea that the runes indicate Sirius' classification as a maximum security prisoner. If you saw the lamp-post standee for the movie, there were more than just the two runes all over it. Quite interesting, and shows that someone on the movie's design team did their research.