If there is anything I hate it's when someone uses and image an artist draws and claims it as their own. Recently saw a drawing of mine being used and the person using it didn't even asked. I sure as hell know that they didn't ask to use it for their own purposes. Here's an idea, maybe ask to use an image, make a request, or pay for a commission. While you're at it, give credit to the artist. Not a difficult thing to do.
Fonrar Thunderclaw is a user of the D&D wiki that had used an image of mine without permission.