Triptych: Four Brothers

"Teenage Mutant Ninja Turtles" by The Geek Gallery

"Lichtenstein Pop Martial Art Chelonians" by Butcher Billy

"The Turtles" by Kristafer Anka

All good stuff, but I love the TMNT redesign by Kristafer Anka. It's worth reading his writeup on his thought process for how he approached each of the turtles.