I have never used a tag to identify image sources. For example, although I post a lot of images that I’ve found on DeviantArt I have made no effort to tag them all as such. If you want to find the artist who created a given image you will have to search for them individually. I almost always identify the artist in a post which should help. So, Google “SissyLillian DeviantArt” should get you the gallery belonging to SissyLillian. If that doesn’t work then try using SauceNAO.com. Virtually all of the images I post can be found using SauceNAO. If SauceNAO can’t find it then there is a button on the SauceNAO search results page to try Google Reverse Image search on the given image. If this doesn’t work then you’re probably fucked because I don’t bother to record where I’ve found each image.