I know how vitally important it is to not plagiarize some elses art.
I have taken down any work that I feel I copied or plagiarized. As a beginning artist I wasn't making any money from my art and I DID NOT take credit for any work that I did not personally feel I created and produced myself.
There were a lot of STUDIES where I copied other art I found on the internet.
I have learned and grown to a point that I now make it mandatory that I include the artist and where I found the art if i am talking about it or using it as reference or using it for a study...
TO THE BEST OF MY ABILITY!!!
If I can't find source for the material I usually don't use it.