How to create a light wall in after effects?
Most light walls in AE are made using a matrix of sorts, rather than individually creating many light layers.  Trapcode Form would allow you to create a 2D array of individual glowing particles, which can then be "driven" by another layer, to adjust the brightness of each individual particle.  A lamp image could be used for the particles, and additional glow effects can then be overlaid to make the effect more convincing. 

There's a page here listing lots of different ways of achieving the same effect:

http://provideocoalition.com/ryoung/story/led_and_casino_text_effects_in_after_effects/