I think a green-pink lizard snake should play the main role.
Really?? You want to make a game, yet you have no idea what it should contain? What makes you think we understand what you want to have?
As limited as you may be, you are still the best person to figure out what to create.
However, creativity is not something you just get out of nowhere. You cannot sit down at a desk with a sheet of paper, and start writing brilliant creative ideas. It doesn't work like that.
Don't try to force it. Instead, write down what you know, or what you want. It doesn't have to fit all together, it doesn't even have to make sense. Just write down every idea that you have about it. Also, each idea that you got, expand it. "I have a green lizard in my game, what would it do? What does it need? What does it want?".
If you run out of ideas, leave it alone for some time, take a walk, and come back later to it.
Slowly you'll find the more interesting ideas :)
Try it, and see what you get.