From the Trello.
Not all chat backgrounds are great viewing experiences. Sometimes they may appear too busy, the colours are too bright, or quite simply you may just find it ugly. Lets face it, we know what MySpace pages were back in the mid-00s.
Idea is that we add an option into the chat options cogwheel (pictured below) that would turn off the custom chat background for that channel. It would then be replaced by the default one. Other channels should not be affected.