jquery.imgbg DEMO2 (customize : center position setting)
This is a demo sample of customizing image base position.
If you want to change a base position of image when visitors change a browser size,
you have to set parameter (left & top) in number of percent.
[upper left / lower right / left:30%, top:80% / etc..]
Images will be resized on basis of the posision which you set when user chenge a browser size.
This page is example of setting basis on lower right corner.