I've selected pretty images to display as background wallpaper on Chrome and Opera browser tabs, but I cannot find how to do this on Firefox browser tab. All I found were extensions to download where you can't pick your own picture. - How can I just upload a wallpaper image? The plain white background is so boring. :( For example, on Chrome, click the little cog on the bottom right and select "upload an image". On Opera, right click anywhere on an empty tab and select "change wallpaper" and a slider pops out where you can pick an image from your computer.