Jamis, I gotta say that (especially in avatar size) the t-shirt pic is no worse than say, the chick in the boat on the river in the bikini with the giant bazongas. In a majority of workplaces, that could be considered NSFW, especially if one of the office feminists walked by while it was up in all it's glory.
For the record, I saw that on Don't Care's link he had Firefox set to super duper extreme safe search and the t-shirt pic still came through.