If you are wearing crystal plate mail over a shirt, you can still read the shirt, because the mail is transparent.

Tourists encounter a new shop, a gift shop, on dungeon level 1, possibly built around the entrance stairs. The gift shop stocks mostly useless items like fake Amulets of Yendor, juice and candy bars at high markups, plastic figurines of low-level monsters, and T-shirts (which are much less of a big deal to the Hawaiian-shirt-wearing tourist).

You can wish for specific text on a wished-for T-shirt by specifying “t-shirt which says xxxxx”.

Straw golems have a smallish chance of dropping a T-shirt.

An artifact T-shirt that provides free action when worn, but only if no armor is worn over it.

Make T-shirt messages not depend only on the object id, so that two shirts generated shortly after one another don’t have predictable messages.