Maybe you're going about this backwards.
I'm working on a similar project and when I started, I visualized what The finished game would be like. What kinds of modes would it have? What kind of features would it need? How would it flow from one song to the next?
I decided that the playfield had to have a kick out hole to lock the ball, drop targets, a spinner and a set of lanes. I wanted the game to have a classic late 1970's feel. Then I looked for games that fit the criteria (excluding rare titles) and decided that Flash would be the perfect donor game to re-theme.
So my advice is to start with the ending in mind. Visualize your finished game and then scour the IPDB to find the right match.