According to C|Net Ask Jeeves improves image search by adding;
New sophisticated image recognition technologies measure attributes such as image type, shape, brightness and contrast level to determine picture quality.
It is hard to tell from the naked eye, so lets do a search on Danny Sullivan. At Google the first result has nothing to do with the Danny Sullivan I was thinking about. But at Ask Jeeves, bingo, the first result is the Danny Sullivan I was thinking about. Of course that is just one search and maybe Ask just got lucky. :)
Forum discussion at Search Engine Roundtable Forums.