There's a neat new background image tool in global styles, allowing you to place a site wide background:

The tool is similar to that of Group or Cover background images:

Site	Group

It diverges in a few places, and both can benefit from a few improvements:

• In both cases, the tool should be called "Background image". It's currently just "Background" on the site wide option.
• At the moment adding a background image to either have different defaults. Site wide it defaults to "Fixed". This is likely a bug, because it holds helptext that suggests of "Cover". Both should default to "Cover".

Finally, the "Fixed" option is easy to confuse with the "Fixed background" property of the Cover block:

One is a fixed size, another is a fixed background attachment. In both cases, the word "Fixed" is the source of confusion. What's a good option there?

One option is to rephrase the option to "tile":

• "Cover" would remain as is, and default. Same with "Contain".
• Tile would still reveal width and repeat controls, but would these would be output as new row, with a "width" label, and instead of the help text saying "Specify a fixed width." it would say "Image has a fixed width."
• A default width of 50% would be assigned. This would also immediately have a visual effect in the canvas, whereas now, you have to enter a number first. Percent may also be a neater default unit, than px.

Figma.