This already exists in the player (though only as a option in the menu, not as a hotkey). But there are sometimes reasons not to display the background image in a level, even to users who usually want to have background images, e.g.
- I think the background image is ugly.
- The background image doesn't fit with the theme of my specific level, even if it fits with the overall theme of the style.
- Parts of the background image are particularly misleading in combination with my level. So I expect that players gain more in terms of playability than they lose in terms of nice visuals.
We keep lots of options because level designers should be able to decide how their level should look like, cf. fake, inverted or only-on-terrain objects. So we should as well accept the wish of level designers who think their level should not have a background at all.