Choosing subjects for your microstock images is an important step. How could I have visibility among thousands of photographers ad millions of images?
You have a beautiful 'red rose' picture and you want to sell it in the microstock market... before try to see how many similar images are already in the stock agencies:
Dreamstime Search results: 26,823 images.
and then try the Rob Davis picniche.com tool for assessing the supply and demand of online stock photography images from microstock sites.
Here the likelihood of making a sale for a 'red rose' keyword phrase image:
PicNiche Rating (all): 0.93 (Rating < 10 is BAD)
If you have a stunning image maybe the chance of making a sale is higher, but generally it's better to find something else with more appeal for the buyers, find your NICHE photography.
Wood pellets for stoves, alternative energy related subject, is my niche. Here some numbers:
Dreamstime Search results: 31 images.
PicNiche Rating (all): 1560.60 (Rating > 100 is a NICHE) Awesome!! ;-)
My best seller wood pellets image at Dreamstime
Let me know if you have a winning niche or if you are "flower and mountain landscape" best seller photographers.