There are a wide variety of uses allowed when using an image licensed as a free stock images.
Commercial/Business Use Allowed
When a photographer or illustrator has set a license on their free image to allow commercial use, then you can use the picture for your business website, blog or whatever else your business has an image-use for. Some artists granting a free commercial license for their images also set an earnings limit up-to which you can use a free non-commercial image, once you earn more than that amount you have to purchase a license for that image, usually around $50-100 a month or so.
Derivative Works
Usually it is denied by a free image license or terms of use you may not make use of a free stock photo to make your own derivative images (a similar image containing the original one you found or based upon that image). The best way to figure it out, is if any part of the free stock image is noticeable in the resulting work created, it is definitely a derivative work and as such has to comply with the license or usage agreement of the original free image.
Distribution:
For most free stock photos or other free images, the right to distribute the image is almost never granted to anybody using the image.
My Free Stock Images Provider
Stockpiggie.com is a part of Templatepiggie.com. Stockpiggie.com is a marketplace that allows users to offer, sell and buy digital items ( photos, graphics, video, and audio) a variety of pricing formats and locations. The actual contract for sale is directly between the sellers and buyers.
New content is continually added to the Templatepiggie.com archive, so there is always something new!
All graphics and files provided on Stockpiggie.com come with the right to use them in all types of projects. There are absolutely no additional fees beyond the price which you pay in our market.