However, this is something I feel should be said, especially on this trashy website.
Weheartit/Pinterest/Instagram/Zerochan/Google are not proper art sources.If you don't have the original artist's permission to use their work as a header, story image or avatar,
this is art theft. Saying "I didn't make this image, credit goes to artist!" isn't enough.
Pixiv.net is often the primary source of where someone's art is from. Since it's easier said than done to find an artist on a foreign website, use
this to find them. If no results come up, then it's either on Tumblr/Twitter/Weibo/Even Deviantart.
Can't find a proper source?
Then don't use the art.
Make sure to check and see if they already don't permit reposting. (It's possible to translate a page if you use right click) If there isn't clear refusal of sharing their art, then follow
these instructions to get their permission on Pixiv.
This isn't hard, people.