Only a couple of them have a photograph, and you wouldn't know what it was a photograph of unless someone told you.
Only half-a-dozen or so have pictures rather than symbols, and half of those wouldn't be recognizable unless you knew what they were. The others are pictures which are also simple well-recognizable symbols, such as a lightbulb to stand for a good idea.
The major and commercial sites which could afford a graphic designer almost exclusively use symbols or one or two letters rather than trying to summarize their content in a picture.
You've got a 16 by 16 canvas, you may be asking the impossible. If you really want something more expressive, what's wrong with my fish icon?