Which resolution is the best for the background image to be spread and not centered

Summary:

Hello,

I'm working on the system's appearance, I came across the documentation that says the perfect size is 1024 by 768.
Unfortunately when I use such a picture it looks centered and pasted. beyond that, the system apearacne comes out of the box with redwood perfect size picture.

How can I solve this?

recommended resolution:

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):