The front of the Slurpee cup features Luke Cage in his glorious original costume designed by John Romita Sr: steel tiara, yellow shirt, chain belt, etc. He looks angry! You would be too if you were framed and had skin that was steel hard.
The back of the cup doesn't recap his origin from Hero for Hire #1. Instead it explains why Cage now calls himself "Power Man" -- Marvel's attempt to make him more of a straight superhero than a street-wise character. Cage says:
I used to be called Luke Cage, Hero for Hire, but I dropped that name after I realized the guy with the money isn't always the guy who's right. So now I'm on my own and you can call me Power Man!
Where did the Romita drawing on the front of the cup come from? It wasn't used on any cover. No, it came from a concept drawing of Luke Cage that Romita executed. It appeared in Marvel's Bullpen Bulletins announcing the debut of Marvel's newest black hero.
On the splash page of Hero for Hire #1, George Tuska probably took that drawing as inspiration for the character's first appearance. Or maybe it was the other way around and Romita executed his drawing based on Tuska? I doubt it as it seems that Romita designed the visual for the character. Nuff Said!