Image links and regular images look exactly alike, making it difficult for someone to figure out that there's a link there. I'd like to suggest a minor style change, something like:
There are a few different options, but they are basically:
Images links can have borders: this would make it easier to see, without hovering the mouse on them, that they are links. The downside is that it might not look good.
Image links will generate a drop shadow when someone hovers over them. Yes, I realize the cursor changes, but this would make it clearer.
What do you think?
PS: I realize SO doesn't use images a whole lot, but the newer SE sites might.