Is it possible to add background support for New Tabs? #1062

I'm editing my theme and have it near perfect but the one thing that I'd really like to change isn't supported - the background of the New Tab page.

There is support for adding backgrounds to the top bar but I feel like intuitively this should also allow you to pick a background image for the New Tab background in the same place as well. Chrome, Opera GX, and others have support for this kind of customization, so I was hoping that it could be added.

I added references to what is currently implemented. The "New Tab Background Color" option only allows for flat colors which is pretty meh. It's ability to change transparency doesn't do anything since there is no image for it to overlay for dynamic effect. There is also no way to change the color of the pinned shortcuts so styling a cohesive theme is frustrating.