Okay, so I have access to someone who knows NOTHING about games. NOTHING.
Showed her a Mario cap, she did not know what it was.
So, let's expolit this all we can.
I showed her this: and asked her what she thought the game was about:
After about 7-8 seconds, she said, "Well... it looks like... is that the back of a car? -- is it a car driving game?"
So, drop your cover suggestions here and I'll report back.
It would be hilarious if she starts to describe every cover as, "A porn game with..."
"A porn game with a fish with a big mouth?"
"A porn game with a boy with a big stick?"
Video games are borderline porn anyway, so she'd be right.
Well if she's going to think all games are porn, you might as well show her this:
I just watched a gameplay video of Portal Runner.
Why didn't I buy a PS2 back in the day? This is why. 
I still in tend to play it one day.
It was a blockbuster exclusive IIRC (available for purchase only at BB).
And one more for the "gaming as porn" arguement:
I was at a Fry's Electronics where there were Playboy models signing this game.
I did not do it.
I regret it more than anythng more I have ever done in my life. Including the time I bought Argyle pantyhose and wore it under my clothes for 4 months.
Okay, now you guys are perverting the original goal. Stop jerking off and post some traditional game covers.