Support imageless backgrounds
Would be good to support solid color backgrounds to avoid loading a big image (current city default background image) and to create a more clean "professional" look. Solid colors can be derived from theme so they'll work with any theme whereas images require picking a suitable image for whatever theme you're using.
We want to keep the option for users to pick their own background image, as well as for admins to pick a default background image for better customization. The question that pops up is, how do we want to manage situations where instance has a default background image set, user with a custom background removes their image. Does the user get blank background or instance default? We can't really know in advance.
Another thing I was thinking of, when we have the background color, we should be able to let user adjust the opacity of the background image, to blend between a themed background color and a custom personalized background image for a good tradeoff. It would create kind of a weird situation where background image is stored on user but the opacity of it is stored in theme, maybe it's ok?
Comments welcome.