A while back, someone proposed a transparent case, and nrp said it’d be unlikely we get a transparent case due to the difficulties of making the plastic rigid enough while still fitting the form factor (Clear Color Shells for the Framework Laptop! - #2 by nrp)
I also know that dbrand happens to sell several skins for the Framework laptop already that allow us to change the outside appearance. A while back, they did a special promotion for the OnePlus 7 Pro where they showed the internals of the device on the skin, so it looked like you could see through it, even though it’s just a skin (here’s what that looked like)
I know there’s probably little chance of this happening due to the complexity that would likely be required in making it and dbrand probably not doing special editions very often, but I think this would look super neat and transfer really well to the Framework!