Randy,
I think it really depends on what you need it to be. Mine is 1280 x 425. I chose that size because the laptop I use on the road has a maximum display width of 1280 pixels. The background photo I use in preview is actually two photos stitched together in panoramic fashion to show the entire front yard and house. Once I proportionally resized the stitched photo to fit the laptop's display width it ended up being 425 pixels tall.
Greg
