I used flexible self-sticking LED Strips with 60 LEDs per meter and just put them into the nuts of the aluminium profiles. They are even flat enough to fit between the z-axis wagon and the flat face of the aluminium profile. This way it's not possible to look directly in the LEDs (they are quite bright).
I also put short pices of the stripes (3 LEDs) directly to the backside of the printhead to have proper lighting when the head moves.
The switch is right next to the display unit but not illuminated yet
