Almost all micro stock image sites offer a feature called light box. What is a Lightbox, you ask?
A Lightbox is a place for you to group you stock images by a criteria of your choice. This criteria can be based on a common theme to the images, a similar feel or just because you want a certain friend or client to view those images together. If you really want to get a glimpse of a goof Lightbox, see jerryhat's great Fruit Lightbox on iStockphoto.
Choosing to place several images together brings you many benefits:
The micro stock customer will see more of your images when he searches Lightboxes
Some micro stock image agencies place several Lightboxes on their front page. So you increase your chances of getting to the first page pf the micro stock site, and by this increase your changes to sell. See shutterstock's home page fr example.
You can send a bunch of images to your clients/friends together by referring them or sending a link to a Lightbox.