I suppose you already know of the illumination bar bug that enables you to have the illumination bar's light dancing with the screen off or when out of the walkman app. If not, all you have to do is make a shortcut of the walkman app on a homescreen, have something playing on the app, and then while on the screen with the shortcut, tap the walkman app and then quickly tap the home button. Now after you've done that the illumination bar will work out of the walkman app and/or with the screen off.
Now on to the new fun stuff I discovered. Install poweramp(haven't tested with other music players) and do the bug mentioned above. Make sure the bug worked(if you're on the home screen and the illumination bar lights up with walkman playing it worked) and then just go to poweramp and tap on a song to play. Now you just caused another bug, a more interesting one. This time the illumination bar works with (almost)any sound coming out of your phone. For example the light will dance with a game's music just like it did with walkman. The only 'downside' is that the colour will always be that of the song that played on the walkman app before you played the song in poweramp.
Illumination bar API... lol
Android version this was tested on is 4.1.2, build number 12.0.A.2.254