I disagree that we need such thing as t-shirts to attract more members. I mean, it's not like getting more people is a central question anyway right? I mean, even if it was, it is so niche and specific! Few people would know what the tees are even about, much less go through the trouble of googling it. But as long as you are the one banking the confection of those shirts, I am neutral on actually creating such shirts. It's your money, do what you want.
That aside, it'd be cool to have a shirt with M' (255) or hPoké or LM4! They are really distinctive for glitches and big cuties ( ^ 0^)