Digital Underground with Tinfoil Hats,  
Let me just show @Haakon Meland Eriksen (Parlementum) and @Adam Robertson this right quick and then y'all can carry on... #coding

background-size: cover  is good if you want the image to fit into your div no matter what size, but it can sometimes cut the image off.
You can also do background-size: contain  which will keep the image at scale, but wont always cover your div. If you use contain be sure you have background: url(blabla) no-repeat;   set, or it will repeat.