The LEGO Tower Bridge is a beautiful set. To add some "Wow-facor" you can easily add some LED light into the bridge.
The small transformer can easily be placed in the basement of one of the two towers.
One LED-strip goes in each tower.
Each walkway gets a LED-strip. To accomplish this, you have to rebuild the inside of the walkways a little. This can be done with the original parts.
...and: You're done!