Why on Earth would you want to use framesets?
First of all, I can't see how you could get the result you are looking for if you are using framesets as a frameset is a collection of independent pages -- so, there is no way that a client side event like rolling over a link can effect something on one of the other pages in the frameset.
If you think you have any good reasons for needing framesets, please let me know and I'll give you the alternatives to them (though there are some extremely rare situations where a frameset is the right solution).
As for the effect you are looking for, a little JS on mouseover to show/hide a div would provide the effect you are looking for, esp. if you preload the images. See my nasty old site at SitesbySean.com for an example to follow (though I'm showing/hiding text rather than images, but same difference).