Blocking Google's New Preview Page

We're trying to block all images from all sites except those designated to be exempt from filtering. We've given up blocking all of Google's thumbails, but we've managed to block the vast majority of them. However, recently Google has implemented a kind of "page preview". When doing a Google search and coming up with a list of terms, if one hovers on the search entries on the left side of the browser, a preview of the page appears on the right-hand side, complete with all images (about thumbnail size). Even if the web page is in a blocked catgegory, say adult content, a preview image of the web page will appear on the right side of the page. Of course we are blocked from going to the actual web page, but it is clearly visible in preview format. We have search filtering enabled in Websense's settings. We are using Websense Web Filtering v7.1. Does anyone have a solution as to how to block these images of web pages that appear when hovering over the search entries? Thanks. Mike B.