If you use the image I linked, here is the person you should give credit to, and the URL you should paste into the comments: https://derpiboo.ru/tags/artist-colon-viwrastupr
If you make changes to the base image, make it clear that credit for the "base image" goes to the artist. In other words don't say that your edited image was done by the artist - they hate that. Plus, you want credit for your enhancements, right?