The spiderman shirt makes much more sense as a clue for blue mage. Spiderman has probably one of the most famous origin stories of any super hero - he's bitten by a spider and receives spider-like powers.

Sam Raimi is a has-been director of a nearly 20 year old movie series... If it's a clue for Samurai it's a bad one that isn't in keeping with any of his other tshirt hints.

There are a lot of people who want/expect samurai who are suffering from confirmation bias.