When an image is available under a Creative Commons license, you are allowed to use that image for non-commercial or commercial use (depending on the license) provided you have given proper credit to the owner.
Wildlife photographer Kalyan Varma has sent a legal notice to an Indian Newspaper as they have used one of his CC-By-SA licensed photographs without attribution. The newspaper probably found the photograph through Wikipedia but never credited the photographer.
If you go to my website, you will realise that each and every photograph of mine is under the Attribution-Noncommercial-Share Alike license (Freely copy, use and remix the photograph for non-commercial use). Unfortunately Wikipedia insists on a CC-By-SA license (Freely copy, use and remix the photograph for commercial use as well).
..I released one of the photographs under CC-By-SA. So its free for anyone to use, remix, etc (even for commercial use) as long as they give the attribution or credit. link.