Without providing accurate citation information, the practice of cutting and pasting images is nothing less than plagiarism (or theft); it is unethical, and may be illegal if it violates copyright law.
This ties right back to what I learned in my first-year composition class about how just dropping a URL under an image isn't enough. We had to practice full image citations in APA or MLA format, which felt tedious at first but really helped to show how easy it is to accidentally plagiarize if you don't do it correctly. I didn't see it as plagiarizing originally, but I learned the rule of law and integrity of it.