@OP: here is iStock's definitive standards manual for keywording for iStockphoto:
http://www.istockphoto.com/article_view.php?ID=227

1200 vectors like the ones you showed us = $300-$500 per month approx, if you are on all the major sites I would think.

It could be way more, you'd just need to see how buyers at different agencies respond to your work.