I received an email from Stijn about displaying image thumbnails in UCM. Content Server comes with a search results template called "thumbnail view." Stijn commented that the thumbnail view was useless because all the content items used the same thumbnail, even if they were an image. This doesn't seem very useful... fortunately UCM doesn't have to work like that. Images and PDF documents can display a graphic thumbnail, here's how...
Thumbnails come from three places. The first place is an icon matched from the dDocType metadata field on the content item. The icon is useful for helping users to quickly identify content by type, but as Stijn pointed out, it is useless for searching for a specific image. (The icons can be updated from the Configuration Manager's "Options" menu, choose "Content Types.") This is the image you see only if no other thumbnail is defined.
The second place is from IBR (InBound Refinery.) IBR is used to process and convert content to different formats and this can include the generation of thumbnail images. The thumbnail is generated at check-in so each content revision gets one thumbnail. Go to the Configuration Manager's "Options" menu and choose "File Formats" to add or set the jpeg and gif extensions to use the ImageThumbnail conversion. Then tick the "Create thumbnail only for select graphics" option on the "File Formats Wizard" page (from the Content Server "Administration" menu under "Refinery Administration".) Finally, tell IBR how to generate the thumbnails on its "Additional Renditions" page. To change the thumbnail size, go to the Admin Server's General Configuration and add ThumbnailHeight=80 and ThumbnailWidth=80 (but it only applies to new checkins - use Archiver to apply retrospectively.) IBR is required for any content processing so it is worth installing, even if just for thumbnails.
The third place is from DAM (Digital Asset Management.) DAM is an extension to UCM that can create multiple renditions of an image, including a thumbnail rendition. DAM is installed on both Content Server and IBR and it requires some third-party software to perform the conversion, such as ImageMagick and ImageAlchemy (more info here.) DAM is probably overkill if all you want is thumbnails.
One final tip - you can force any search results page to display thumbnails by adding &listTemplateId=SearchResultsThumbnail to the URL. This is useful in the contribution editor for when the user is trying to insert an image because it overrides whatever view they have configured.