We've been talking about what type of tattoo people would want (or at least ZaXeriaw) and where here http://www.lucasforums.com/showthread.php?t=181678
, but as for a specific logo which I could imagine would make tattooing it on someone's body easier, i've been looking around.
So far i've been browsing the DOD (http://www.grim-fandango.com/index.php
) for material,
The billboard/thingy on the front of the DOD building might be a good "logo"
There are also the logos for sproutella and the LucasArts Skeleton
On the DOD site Diney was able to do the latter in a larger formate, so maybe their work might be easier to work off of.
Also CiceroX's work would be a wonderful tattoo, even if it is not neccessarly a logo.
Finally there is always the game title in its GF font.
If you need bigger pictures of the stuff above that's in game, I would be more than happy to make big screenshots for you and post them here.