It's hard to guage annually as we've only been going a year and the difference between the early months and the latter months is significant. We run our microstock through our website design / graphic design business, and it's currently running at around 20% of our total revenue. It's good income because it's near-passive once the images are up on the sites, but for us non-professional photographers I suspect we find the going harder than professionals would. We work on it only during slow periods.
Well your avatar is nice, so you can't be all that bad