I see a lot of the work I have created for Marvel licensing popping up all over Deviant Art with no credit given to me or the originating concept artists. If you are not aware of who that might be, that's perfectly fine. However, a simple clear indication that you are not the originator of the art is the least you can do. Showing respect for other artists in the industry may even help to get you real work one day on these projects. However, when you fail to exhibit basic professionalism that will certainly speak volumes to any hiring managers.
When I'm personally aware of who has created any art prior to my working on it, I will always acknowledge that artist with a credit to their work. (if I have not done so, I was simply unaware of who did the work, so please let me know)
Simple request: Can anyone who is posting my work, offer the same courtesy and simply add my credit to the imagery? You may not realize it but accepting credit for work that you did not do is illegal. There have been a chain of artists and decision makers who actually brought this imagery to life. To ignore these individuals hurts us in the long run because our hard earned contributions are diluted by your stolen exposure.