I have the NZXT H440 (Red/Black), its a beautiful case but the NZXT logo on the PSU shroud just ruins it IMO and I would like to remove it and put in a custom design, but what material(s) do I need to replace the NZXT letters and make it a nice smooth finish so I can put in a custom design?
I suppose you could cove the entire PSU shroud with this: LINK
If no, you will have to construct something from scratch, a sheet of aluminum, and bend it to match the shroud, then you can send it off somewhere so they can cut out a design of your choice.
From pictures it looks like there is screws to secure the illuminated logo from inside the case. I suppose you should check that out and hopefully the part that only enshrouds the logo can be removed and the metal be intact. You will still need to get some custom shroud going for around your custom design. I would suggest seeing if there is someone local or if possible find someone cheap to 3D print out your custom design and you will just need to insert something to carry the light on your custom logo, if you wanted it illuminated.