Annnnnd: happy anniversary to my older sister and her husband! I can't believe next year is the big 2-0 for you guys.
On with the wallpaper...which should really be called desktop pixels:
[TO USE: Click on the resolution that's closest to yours to open the picture (you can check your screen resolution here, although I've heard it's not always accurate). You can then right-click on top of the image and "Set as desktop background..." or whatever the similar wording is in that menu.]