I’ll be making more preview sets soon. Master system, SNES, Nes, and GBA will most likely be the next sets with more to follow if there is enough interest.
The 3d boxes you found are nice but are lower resolution than the ones I’ve made myself and I’m trying to keep a consistent look. I have a source of nes scans so I will make a high resolution set of 3d boxes myself.
I have made several programs that I use to generate these previews. One for generating the 3d boxes and another program that combines all the images together and finally one to create the gamelist.xml needed by emulationstation. Unfortunately they aren’t suitable for sharing as they aren’t at all user friendly, I have to modify the code for each new system. Also everything has to be renamed so that all the images match correctly so it does take a bit of preparation to get everything ready. Finally once everything is ready I use a png compression program to keep the file size as small as possible.
I may at some point get the 3d box rendering program to a state where it would be releasable as it would be useful for quite a few frontends and commercial software for doing this is expensive.