So the easiest way is by using SGDBoop [www.steamgriddb.com]

After installing it, you can go to the Grid Collection [www.steamgriddb.com]

On the grid collection page you can simply click "Apply with Boop".


Afther doing that, the background and logo will change immediately, if not just restart Steam

You might need to change the position of the logo, you can do that by right clicking the background and selecting "Adjust Logo Position"


Alternatively, if you dont want to use SGDBoop, you can download the .png file and apply the images manually, also by right clicking the background and selecting "Set Custom Background" and "Set Custom Logo".