As of 2015, some sources for Snoopy desktop backgrounds include DesktopNexus.com and HDWallpapersCool.com. To access the Snoopy wallpapers on DesktopNexus.com, navigate to the website and enter "Snoopy" in the search text box at the top of the page.
On the search results page of DesktopNexus.com, click a wallpaper thumbnail and click the Download Now button on the right-hand side of the page to display a larger version of the wallpaper. Right-click on it and select Save Image As to save the image file or select Set as Desktop Background to use the image as the wallpaper.
Alternatively, navigate to HDWallpapersCool.com, enter "Snoopy" in the search text box at the upper-right corner of the page, and click the link to Peanut Snoopy 2015 Wallpapers in the search results to access the wallpapers.