What is ISOLATION. It reffers to isolated objects in a photo or illustration. Isolated images get more views and more sales. Why ? Let us remember that most of the buyers are designers. Most designers probably put your downloaded images in a website or media article. It is common sense to choose a nice isolated object (usually on white background - this is another important key to success sales) and put it in your article, rather than using a whole composition that would fit better in a frame on the wall.
Here is an example: Lets say i'm a buyer and I need a picture with cash for my new "increasing wages" article. I will write this article on a white background (as most do) so I will choose a good picture such as:
All of the above are good examples of isolated images. White background is important since most articles are written on white then you get your picture integrated perfectly. Now find for yourself a bunch of non-isolated images... try to make a difference.