Is it common for your images to rank well (i.e., to show in the images near the top of the SERPs) even when your PAGE for that keyword doesn't rank in the top 10 (or top 20 even)?
I have found that for several keywords on one of my sites that search queries in webmaster tools shows me at an average position between 1 and 2. When I check those search queries, it turns out that it is often an image instead of a page listing.
Is that a sign that something might be wrong with my site? Why wouldn't the page that the image is on also rank in the top 10?
Second question: Do people find that the click-through rate is higher, lower, or about the same for their image listings as opposed to their page listings?
I can only address the first question. Image search ranking is not connected to organic search rankings in any way that I've ever seen. They are controlled by separate Google teams, each under separate management.