It would be great to find image by their similarity.
You may know that an image is better than a lot of words.
Some type of image are much better describe by themselves than by keyword. So it would be good to be able to search for the similar images, whether you are looking for duplicates, near duplicates, or group of looking alike images to put in a collection,...
as well it would be good to have a small sketch black board that would be used to find similar image. Put a red back ground and all image with red dominant background appear. Put a orange circle and all susnset image appear,...
a bit like this soft: http://www.imgseek.net/
or even PSE10 which has it in its cataloging function. Why not lightroom?
feature request to vote for is here: