You could download GoldYoink and make 95 more levels for that game, and maybe add some improved graphics. Levels for that game are really easy to make... just place tiles -- no need to worry about sprites or paths or functions because they're all handled in script. Maybe you could even add some new features to it while you're at it.
I don't think you have to have a really clever idea to start a game. The idea I started with for Rolly was just make a really simple game with simple levels and expand on it. It doesn't matter what the game's about or who the characters are. Actually that's the whole point that the title of Rolly the Purple Ball is making. It's just about a ball that puts other balls in places to get energized to get to the next level. And I think it's fun anyway. This kind of game doesn't need a particular story or character to make it fun. Scrolling games that waste too much time trying to tell a story often leave out a lot of gameplay. It's fun because you play to accomplish tasks, not because of what the story is or who's in it. So as silly as the title sounds, there was a point in it

. Just make up anything and expand on it whenever you discover another feature you'd like to try out. Take a look at the
clever ideas topic and use some of those ideas in a game.