Here's how you can see preview images of sites in Google's search results. Google recently removed this feature, but you can get it again with this free extension for Firefox.
1. Go to the Preview Peek extension page.
2. Click the Download Now button to install it to Firefox.
Here's a description of Preview Peek for Firefox:
"Shows preview images for Google search results. Each preview image is shown on the side or below the respective search result. The preview images are the same with the ones provided by Google on the right pane of the page. The benefit of showing the previews with the results is that the user can immediately see the target pages before opening them. Available options: - choose between side or bottom position of the preview images, - choose between small, medium, large, or full size images (for bottom position), - open preview image links in new tab."
For more, see the original article at the link below.