Here's the back (on the white/light shirts only, no back printing on dark shirts):
I also made some 3×5 stickers, so you can edit signs to add semicolons where they ought to be:
And, of course, a membership card:
Although I'm not happy with the wording of it. Anyone want to suggest new wording that actually, you know, includes a semicolon?
I was thinking that the Semicolon Appreciation Society's bylaws should be like those of humorous WWII servicemen's associations, with riddles and having to forfeit the price of a drink if you can't write a sentence including a semicolon on demand. Suggestions for further bylaws entertained in the comments.
Thanks are due to Garth, who recklessly encouraged me, and India Amos, who suggested the completely wonderful Cooper Poster font as the one that included the platonic ideal of the semicolon form.