Here, the_siobhan and I will demonstrate.
This is actually camera-flash from taking a picture in the mirror, as described here.
I usually use it for posts about creating things.
This one's me in the bath, taken by one or the other of my parents. Oddly, the original picture (at least the scan they sent me) is about the same aspect ratio as the icon. I'm not sure if they cropped it or if it was originally a Polaroid or something.
I often use it for comments where I'm giving someone sympathy, because the hand full of bubbles looks sort of giving to me. I also sometimes use it as my "innocent face", or when I'm just talking about babies.
Here we have a female red river hog from the San Diego Zoo. I took this picture the month before I started this LiveJournal, because I got the LJ account on suggestion of folks I'd met at the San Diego alt.polycon (hi, folks!).
I put this on posts in which I am particularly weird. It also turns up on comments about bacon. I used to use it for grumpy things, but now I mostly use the next icon for that.
In practice it signifies sardonicism more than suspiciousness.
This is one of the things I made for the first round of Tiny Art; its finishing is described here. I'm terribly pleased with it.
I use this one when talking about things I've created, too. It's been going on a lot of the posts about the Nobilis game I'm running.