help think of a T-Shirt Design?

hey, for a school thing, we have to make a T-shirt design for an event where you ride your bike to school for a month to help the planet, you get prizes and stuff for each day that you do...

but my question is, what would a cool T-shirt design be?

it should be something about helping the earth, or loving the earth, and kind of about a bike? but the theme is "Define your Life, Ride a bike, Save the planet"

we have to make 4 small pictures and my three ideas are:

1. an earth riding a bike

2. an earth with bikes all around it (like people holding hands, only bikes)

3. a bike with earths as the wheels

4. so this is where you come in, help think of one more design

also tell me what you think of my others

thanks!