Ok not sure if this counts as a request or bug. When I tried changing the theme I didn't like the results, but there is a button or option that I can see to restore the Campfire default. This would allow people to start fresh especially if they've saved changes they no longer like.
Using the dropdown menu in the top right of the theme modal, you should be able reset the theme to one of the default themes. Let me know if you can't find it or if it doesn't work for you though!