The first plot is a histogram of total pixels. Most frequently, images are under a quarter gigapixel, but there are quite a few between 750 and 1000 megapixels. And it has been uncommon to take images larger than a gigapixel.

The next plot is a histogram with 2-D bins, showing the frequency of width and height (in pixels).
The more popular imaging modes are colored brighter. So the most common dimensions are around 20,000 by 40,000 (the yellow box). Most images are the full width (20,048 pixels), followed by half width, etc (the columns). This is simply a function of the binning (subsampling) modes, but can change due to missing or unusable channels. However, there is a good deal of variability in the heights, which corresponds to the exposure duration (and also the binning). At least one image had over 120,000 lines!

These plots were generated with ploticus, a free-software plotting utility.