Step 1

As you know, steam lets you showcase a main artwork, and some side artwork. This results in a split to the right of showcased artwork.Now to add a second split to the left side of the showcase, we need to add it to the main artwork. Start by downloading this overlay image: https://imgur.com/a/MzKlx Once you've downloaded the image, open it up in an image editing sotware and put it a layer above your main artwork.