Heya,
There are multiple ways to skin that cat, so to speak. I’m not sure what the best approach would be based on what you’re wanting.
If you want to use the same image as your using on the home page (uploaded via Appearance > Background), then you could remove the overlaying background on interior pages via the stylesheet.
If you’re wanting a different background image per page, you’d need either a plugin or some custom jquery scripts (that’s if you want it to be a “stretch” image). If you want to use the page’s featured image as the background, that’d be a different approach.
So, not sure what direction to point you in as I’m not sure which scenario you’d like to accomplish. Either way, it’ll take CSS edits at a minimum, possibly more.
Cheers,
Carrie
p.s. Since your question is less specific to Winning Agent and more general theming customization, you may want to have a look around the StudioPress forums as well to see if someone’s asked a similar question. 🙂