This is a great step-by-step post on how to properly credit artwork shared on Tumblr & throughout the internet! If you see uncredited posts floating around the internet, feel free to send a Note to the author of the post and encourage them to properly credit and source the artists.
posting without a source is unfortunately pretty common, but it doesn’t have to be. with a few minutes of hunting, you can make sure the artists you like get credit for their work! :) hope this is helpful.