Go on your browser and log into steam on there. From there on you move onto YOUR Artwork section.

Next you click on Upload Artwork and then cick on Not Game Specific.

Now Press F12 and open your CONSOLE and copy paste the following command: $J('[name="consumer_app_id"]').val("8870");








Now you can do the usual, put in your image or gif and then upload it and it'll be uploaded as an Bioshock Infinite Artwork.

There you go, have fun!