I don't really use my desktop for anything, so I like having huge icons of my currently installed games there, even though I don't really play most of them regularly. Hell, I haven't even gotten some of the games that seem interesting enough I already have an icon for them waiting to be used!
All the icons utilize either box art, in-game graphics or official artwork, whichever was more suitable or even available for the purpose of pretty icons. Resolution is 128x128 and they are in both png and ico format. The ico's contain an upscaled 256 image, because Windows tends to ignore the 128 one and display needlessly small image.
My icons are mostly for old games, but there are some newer ones too,
especially for series spanning decades.