Literally wants to know the same thing as Phonax XD (love the look of car btw)

https://github.com/TechnologicNick/SteamChangePreview

hey, question, cause you can probably help me with something that I need help with

I've been trying to figure out how to set a custom thumbnail to one of my workshop items, but the internet isn't helping me and I figured I might as well go to the workshop and find somebody that's put a custom thumbnail on one of their own creations. So, how do I do it?