What I was referring to wasn't the change in the image upon rollover, but the "loading" of the images (before they are in the cache). Even on a relatively decent connection, they take a second or so to load and you can see the void behind them.
Is there anything that can be done do show the plain background behind the images and then allow the image to fade in or anything like that (as they load)? I know this sounds kinda like Flash, but I'm looking for a similar HTML effect if possible.
If you know of a website that demonstrates this well, I would love to see.
Thanks for your responses so far!