ImageCacheViewer is a compact portable tool which scans the caches of your web browsers (Internet Explorer, Firefox, Chrome) and lists the images they contain.
A detailed report includes the URL of each image, the browser used to access it, the image type (PNG, GIF, JPEG and so on), the date and time of the image file, the date and time it was viewed, and the file size.
There is no "thumbnail view", unfortunately, but click any line in the report and an image preview is displayed in the lower pane. Right-click any image, select "Copy", and it's sent to the clipboard for easy reuse.
The program has some interesting configuration options. You can point ImageCacheViewer at custom cache folders, which might be handy if you need to check portable browsers. And you can restrict the program's report to only your most recent files, or URLs which contain specific strings, a great way to zoom in on the data you need.
Please note, NirSoft recommends closing any open browser windows before using ImageCacheViewer, so ensuring that all cache files are flushed to disk.