I've thought about getting a tattoo, but I don't know that I ever would. If I did though, I'd probably get an anchor, and maybe the founding date.
And I just typed "Alpha Sigma Tau tattoo" into Google to see if I could find any pictures, and this link came up for this t-shirt. I really like it.
http://www.getsomegreek.com/Retail-Item.cfm?org=Alpha%20Sigma%20Tau&orgid=118&categor y=Short%20Sleeve%20Tops&product=Tattoo&gid=432
ETA: some other NPCs and fraternities have the same t-shirt with a slightly different design