Of course I'm never satisfied until every project of mine is stuffed full of lights. This is no exception.
For this project I ran a few segments of Neopixel (WS2812b) tape along the interior perimeter of the acrylic window. Putting the LEDs in this spot hides them from direct view and points them at the shiny parts inside.
I control the LEDs via an Arduino Uno mounted in one of the 3.5" hard drive bays. It receives power directly from the USB port on the motherboard and can be reprogrammed from the computer at any time. The LEDs draw too much power to run off the Arduino so I tied them into the 5V DC standby power of the PSU. Even if the computer is "Sleeping" it will still provide constant power to the USB port and 5V standby.