Ooh, I like the My Neighbor and Cat Dozing shirt designs. It was a tough call to say which I'd prefer. Went with My Neighbor, though, given the Cat Dozing on Book seems to have plenty of traction as it is.
That said, I second the idea of adding smaller merch items like coffee/tea cups to the list; I'd also want to throw water bottles and hats into the idea pile as well, given those can be used/taken anywhere and use the same designs as the shirts. Would it be possible to consider those, or even other little accessories like pins, key chains, or refrigerator magnets?