LaRue Tactical has a lot of screen art out on their site ready for you to download it for free!!! Below is one wallpaper which you can use for your desktop for example. There are many more for mobil devices like iPhone or iPad. Also they have a monthly calendar for 2012 but the April picture is not available yet! So stay tuned for this one if you want to have it.
Check www.laruemedia.com/LaRueScreenArt to get the full feature.