CSS spriting is beneficial for speed in many ways, working in various ways. It combines small images into large ones, reducing the need for more server connections.
In most browsers (not including Opera), it’s faster to decode one large image as opposed to several others, speeding the process up even more. Additionally, space is saved from the overhead of each individual request which can end up saving a lot bandwidth.
The below graph shows how using sprite for 4 images saves data – considering you may have 50 plus images, you can save a lot of space with this one trick!