I have put together preview for visually shaking maps where you don’t get just map layer names, but also preview of layers ! Somehow I couldn’t find any page on internet that would allow you to display layers from GetCapabilities WMS as image thumbnails. I’ve kept this idea for a long time and actually it started with yahoo pipes year ago – why not to visually display GetCapabilities as RSS feed with image thumbnails referenced as media type in the feed ? after little experimenting I realized that the value is in combination of position and WMS information, so the use case is “I am here on this place and hey WMS servers, give me all you know about this place…”
Map Binder can be found on page http://www.sumbera.com/lab/wmsbinder/getcap.htm . Feel free to save it and examine it. I believe that from this point desktop and web readers of WMS layers will display thumbnails for better user experience :).