Allow setting images as background for chats

I never knew people actually liked this, but today my girlfriend made me see otherwise. In competitors like WhatsApp it's possible to configure a background image for your chats. This can be done for the whole application, and also on a per-chat basis.

My girlfriend says she misses this on Element and she likes it as it makes the application more friendly looking and cheerful. So the request is to allow setting custom images as background on a per-chat basis. Offering some default images would be nice but an extra.