Custom background images with opacity slider/vignette

### Your use case

#### What would you like to do?
Custom background images for either each chat, or the whole page(or desktop application). With an opacity slider in settings.

If the user sets the background image to be on the whole page (or whole application) there could be an option to add shadows at places near for example, the border between the channels and chat. and the border between the "room info" sidebar and the chat and basically anywhere there is a major border.
Maybe a shadow on the whole all all sidebars of just the border between sidebars would be good too.

Basically, wherever there is a sidebar that isn't the actual chat screen it could have some dimming/shadow/darkening on the background image. There could also just be shadows on the edges of sidebars instead of dimming the whole sidebar to indicate that it is, well... a sidebar

#### Why would you like to it?
Customisation.
#### How would you like to achieve it?
I have no idea

### Have you considered any alternatives?

_No response_

### Additional context

These are from a discord modification but most of the images are a good example. https://duckduckgo.com/?q=betterdiscord+background+images&iar=images&iax=images&ia=images