Hi,
It would also help if you told me the version of Moodle as well as the version of your Academi theme.
Its quite easy to add a rollover effect for an image, however I would need to know what the dimentions of the images are as these all need to be the same size for it to work effectively.
also...have you already got the link images working?
If so then can you copy and paste the CSS listed for that link?
Thanks
Mary