It might be worth taking a look at the SVG node (there are loads of examples that should help).
I've used it to place an image as a background on the dashboard, then change the colour of what looks like LEDs at various places on top of the image.
Note:
To avoid any confusion, I don't use an LED node, just a circular icon to represent the shape of an LED.
This example is a photo of a mini tower of four RPi-3Bs.
The grey coloured blobs are positioned at X, Y coords over where the LED is located on the RPi.
When my flow is running it also updates the IP address and CPU temperature for each Pi.
