Editor's note: It’s the world’s reserve currency and the world’s most widely-held currency. It rules American pop culture via songs like Madonna’s “Material Girl” and “Money Make Her Smile” by Bruno Mars, not to mention that the dollar sign is the principal bling for rappers’ jewelry. Its look never changes: George Washington has been staring back at us from the one-dollar bill since 1869 and will probably be there forever. Now get yourself a cool Dollar wallpaper and spend wisely!