The only way I know of to stop the flicker is by using a sprite technique. You just put a hover selector on the object and update the background-position attribute to bump down to the second image within the sprite.
Most people use GIF's, but that will also work with JPG's and PNG's.
Search for CSS rollover in google.
This is an example of the css code I use for an image rollover:
background: transparent url(/images/image1.gif) repeat scroll 0 0px ;
background: transparent url(/images/image1.gif) repeat scroll 0 564px ;
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