Hmm thats a little more tricky. You might be able to set up a matrix of capacitance sensors behind the glass. Here is an example of a single sensor setup. Arduino Playground - HomePage
Im not sure if you could put more than one of these next to each other though because that might mess them up.
Do you want the whole pannel to light up when you get next to it or touch it, or do you just want the part under where it is touched to light up?