I was gonna make an infinity mirror based on the 23x23cm IKEA Ribba picture frame. The visability of all the resistors and the contact pads made it look cheap...

So I designed these covers to hide everything but the LEDs themselves. There is only one corner where the contact pads are visible, but with a bit of black paint or tape they're gone. The four pieces replace the inner Ribba frame and the LEDs are sitting in the center between the two mirrors for a perfectly spaced infinity reflection.

And here is everything you need to build your own:

• the four printed pieces
• IKEA Ribba picture frame (23x23cm)
• silver reflective foil (for the front "glass")
• a 23x23cm mirror (for the back) or the "glass" of another Ribba with reflective foil
• 1m LED strip (you'll have to cut off 2 segments)
• a controller for the LEDs
  (This is the LED strip I used with an RF remote insted of the more common IR remote as you can completely hide the receiver behind the frame:
  https://www.aliexpress.com/item/5V-UBS-LED-Strip-5050-RGB-White-Warm-White-Red-Green-Blue-60LEDs-m-50CM-1M/32730953194.html and you can go all wireless with a small power bank as the power interface is USB.)

The covers are designed for a nice fit, but you want to use the adhesive of the LED strip to secure them, and maybe add some double-sided tape to the printed part to keep them from moving slightly.