I ended up choosing five breakpoint based on information from StatCounter:

This is up till December 2012.
Based off of these numbers, my testing, and speaking to others I chose the following options:
/*Monitors Large than 1920px, image has "soft" edges to blend into background */
@media (min-width:1921px){
html, body{
background: url(/images/backgrounds/1920-bg-large.jpg) no-repeat center top fixed #190303;
background-size:100% auto;
}
}
/* Mointores ranging from 1367px - 1920px */
@media (min-width:1367px) and (max-width:1920px){
html, body{
background: url(/images/backgrounds/1920-bg.jpg) no-repeat center top fixed #190303;
background-size:100% auto;
}
}
/* Mointores ranging from 769px - 1366px */
@media (min-width:769px) and (max-width:1366px){
html, body{
background: url(/images/backgrounds/1366-bg.jpg) no-repeat center top fixed #190303;
background-size:100% auto;
}
}
/* Tablets like the iPad 2 and iPad Mini */
@media (max-width:768px){
html, body{
background: url(/images/backgrounds/768-bg.jpg) no-repeat center top fixed #190303;
background-size:100% auto;
}
}
/* At a certain point the Background images become irrelevant as they are hidden behind other elements. Changed to a solid BG */
@media handheld, only screen and (max-width: 640px) {
html, body{
background:#190303;
}
}