Here is a Pikachu themed lightbox. Individual STL files included also. When imported into Bambu studio or similar slicer, import them as a single object and then assign the desired colors. The face is .6mm thick to allow for good light penetration. There rear covers are 22mm height. Either helps prevent LEDs to be seen and also allow for running 2 rows of LEDs. 11mm cutout to allow for easy wiring of LED lights.

If you don't want to change the name in Fusion 360, included is another version of just the Pikachu without the cutouts for joing the two “light boxes” together.

Links to the LEDs and connectors if you need to join two strips together vice soldering a bunch.

10mm LED strip (2 pack) https://www.amazon.com/dp/B0BPPJ5HMX?psc=1&ref=ppx_yo2ov_dt_b_product_details

10mm LED connectors: https://www.amazon.com/dp/B08R61MTPR?psc=1&ref=ppx_yo2ov_dt_b_product_details