Memorable rush shirts...
AEPhi's rush shirt from my senior year was a navy shirt with letters in white, made to look like the GAP logo. (Not really a "rush shirt", but they were printed for rush, and everyone wore them at one of the parties.)
Our bid day shirts from that year were an American Express card with "Alpha Epsilon Phi" where "American Express" would go, the date of bid day as the "credit card number", and a giraffe where the centurion would be. Back: "Membership Has Its Privileges"
When I rushed, AXO had a rush shirt that was red with white writing, "Alpha Chi Classic", in the script you would see on a Coke can. Their theme for that party was based around Coca-Cola. (AXO at my school went by AXO, not Alpha Chi, to avoid confusion with Alpha Phi. Some of my fellow PNMs got confused and thought we'd wandered into Alpha Phi's party
)
ZBT did a rush shirt one year with the logo from Zima, substituting the letters ZBT. "A unique non-pledging fraternity."
Theta Chi always had shirts that billed their rush as "Ox Hunt".
OP, the evolution chart thing could still work if you used random Greek letters rather than the letters of any real org. Or, use Ox Hunt!