Model was originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4461246.
GPUs today come in one of 3 widths: single slot, double slot, and now 2.5 slots. The original thing has a 3 slot end plate that would hold any of these but I'm decidedly a minimalist so that just wouldn't do on something that hangs on the wall like a piece of art for everyone to see.
The current GPU in my system is of the two-slot variety so I made this edit to the original. I will also be making a single-slot variety as an update to this remix. After printing, I have verified that the card fits snugly as intended and that even the thickest DisplayPort and HDMI cables I own fit past the slots and into their respective ports.
You will still need to print out all parts other than PCI_Slots.stl in the original from lechukk: https://www.thingiverse.com/thing:4391326
As this is to be wall-mounted in a custom open-air case it needs no connection to a backplane, as such. Therefore, I removed the mounting from the top and smoothed the transition to the PCIE slot bracket for aesthetic reasons.