Steam now allows you to set custom images for all items in your library, including non-Steam games. Here are a few images I have made for myself derived from official artworks and images found on Google Image Search. If you are the copyright holder or original artist and wish me to remove an image, please contact me.
These Gamecube images are the latest updates to the full list of Steam custom images.
I posted a Dolphin emulator logo earlier but it wasn’t good. There is a much nicer one posted on NeoGAF that I’m using instead.
The first item in the list is a PNG template that I’m using for all my Gamecube games. The rest of the images have this banner but I’ve also supplied the clean version of R: Racing Evolution. Also, a warning: Mario and his rape eyes from Super Mario Sunshine are contained in this post.