We are having this function suggested:

currently it does not seem to be possible to search within the thumbnails view of the Assets App. In Magnolia 6, search results are only displayed at the top without thumbnails, and there is no way of restricting the display of thumbnails to search results within the Assets App itself.

It seems to me that this makes the thumbnails view pretty much pointless as soon as you have more than ~100 images in the system. (BTW this is already the case in Magnolia 5 as well)