Some photos are pictures that you allow company to use for a commission. You may receive a flat fee per photo that is acceptable or a commission on each download of your photo. Stock photography companies offer paid memberships to customers in the graphics or photography industry. Their membership fee allows them a certain number of credits that they may use to purchase the photos that they need for a particular project.
There are lots of stock photo companies around today such as:
• iStockPhoto.com
• BigStockPhoto.com
• FotoSearch.com
• SnapVillage.com
• 123rf.com
You can take a look at each of the above to determine which you prefer. One major feature that I like about Shutterstock is that they have a forum where designers request the specific photos that they want. Other sites have forums but none that I have seen make it easy to know exactly what will sell. When you know just what the designers are looking for you will what photos to submit and get a lot more money.