I think what you are asking is if it’s possible to have multiple size images as background images. If this is the case, then it really isn’t worth the hassle. Background images will scale by default, but there is only an option to set one image at one size. For most people, this is more than adequate. Just make your background images about 2500 pixels wide. Optimise the images for the web and just use that. This will cater for most of the larger screen resolutions and will be be perfectly clear. This image will then scale down in size on smaller devices without any perceivable loss of quality. In many cases, you can use images of 1600 pixels width and still get a very acceptable quality on larger screen resolutions.