It depends. Sometimes it may be appropriate or legal to publish an image or text without crediting the author or creator. Other times, it might be inappropriate or illegal to publish an image or text even if you credit and link to the creator.

For example, you can't legally or appropriately use warez, even if you credit and post a link to the creator of the stolen software.

In another example, you could post an image or excerpt from a text for fair use (such as to provide criticism of it) for fair use, and are under no obligation to credit the creator or post a link. For example, I might post a quote or excerpt from a scam website to show people what scammers say and do and such, and tell them what's wrong with it, and I wouldn't post a link or name the scam site as to not promote them. That would be fair use, legal, and as far as I know we all would consider it appropriate.