Forum Moderators: open
You could make the original image display as a background-image, with the foreground being a transparent gif. Then you would use javascript onmouseover (rather than css a:hover) to switch out the foreground omage to one with some content and some transparency.
But that's likely to get very complex, with edge pixels and so on. Until IE fully supports png transparency, I think the best approach is to create a new hover image that is based on the original image. It will give the effect you want, but it will still be only one image.