I've always found the Steamgriddb website to be perfect for changing game covers on Steam, but it has one major flaw, it's tedious to change covers via the website. So I made a mini app to simplify the process.
Below I detail how it works:
Steamgriddb Integration (1)
First you need to create an account on Steamgriddb and get the API key assigned to your account.
Steamgriddb Integration (2)
Then you have to add the API key in the app.
Steam Integration
The app will automatically detect Steam games that are installed on your computer.
Selection of covers (1)
When you select the game the app will load which covers are available for the game, the example in the screenshot is the game Wasteland 3.
Selection of covers (2)
And the last step is to select the cover, the app will automatically take care of adding it to Steam.