Suggestions on LED Matrix with Ping

I am fairly new to using Arduinos, but I have it set up so far with a Ping motion sensor so that depending on the distance someone comes to the board, LEDs will get brighter or fade (thus changing colors). I am interested in making a large signage with frosted plexiglass for a gallery show, and will need a good amount of LEDs in the enclosure. I took a look at the capabilities of using Arduino with MAX72xx but it doesn't seem to enable brightness variation in individual LEDs. Any ideas of how to efficiently tackle this project?

Depends on how large the LED matrix is. The TLC9540 will give 16 LED outputs that can control the brightness.

This can easy be multiplexed into a 16 X 4 matrix like in my project here:- http://www.thebox.myzen.co.uk/Hardware/Mini_Monome.html

That uses RGB LEDs but just think of replacing each RGB with three separate LEDs