Our Single List Results mode is powered by Google and Bing which unfortunately do not include images. (Although you can still use the 'Has Picture' checkbox to filter for items that have images; you just can't see them until you click through.)
You do have one option if you want to see preview images with your results though: our Direct Results mode. To switch modes, just click the Direct Results toggle on the results page. With the Direct results, you view results pages directly from craigslist, complete with preview images and everything else.
Please note that we have no affiliation with craigslist, and we don't have any control over the content of the craigslist windows opened, besides linking to them.