This is a proposal to expand the capabilities of the Cover block (and other blocks using background images) to empower users to achieve more varied visual effects easily.

Right now it's difficult to achieve effects such as text overflowing images. A user could do it by composing an image beforehand using an image editing tool and upload it as a full background, but that is a very poor experience for both the creator and the viewer.

One way in which we can allow this to be done with ease is by having background editing options directly in the Cover block itself. Imagine an "Edit Background" tool that would focus just on the background of the block (fading all the layered blocks and their controls away) letting users reposition and resize the background image at will and include setting a color.

That would allow going from the regular effect:

To a composition like this:

The flow could be engaged using a toolbar button which folds the Cover block toolbar into background editing mode, including color selection: