I realized that I have no idea who even designed Mr. Terrific's costume. I forgot he wasn't a Goyer/Johns creation from JSA but actually from Ostrander's Spectre with Tom Mandrake. But he had a totally different outfit there.
It's really hard to find a publication chronology for him, so I'm just vaguely piecing together that he appeared in the Spectre first and then nothing until the JSA reboot with issue 5 in 99. He had a different costume in The Spectre issues, then has this in JSA, credited to Derec Donovan/Aucoin. I wonder if he was the one to redesign him, if he was working off an already made design(Donovan was a fill-in artist and often main artists will have designs ready), or if it appeared before that and I can't find it.
Just kinda interesting because it's a pretty memorable costume but no clue who even made it.