1: Open rust, prepare the workshop object.
2: Prepare the Icon (size 512x512 pixels).
3: Copy and paste the icon. Rename it to icon.png and icon_background.png
4: Copy it.
5: Go to yur HDD x:user/systemuser/appdata/local/temp/
6: Back to Rust, Click on submit your workshop item.
7: Quick paste the two icons inside the new folder inside the temp foler.
8. You're done.