If I understand you correctly, what you're looking for is already available in the front-end.
Highlight any game, click the [Info] button, select {Contron Panel} from the button under the [Info] button. Once you have the Control Panel PNG's installed in your Control Panel folder, you would see the info on controls and button/joystick/wheel/spinner/trackball layout for any selected game. That is... if I understand you correctly.
You could also have a look
at this site if you need more detailed info.