Leather sea stars (Dermasterias imbricata). Photo courtesy of the National Science Foundation, image 51 in The Marine Life of California's Rocky Shores. Retrieved from: http://nsf.gov/news/mmg/
Remember, you need to cite any and all images you use, just like you would a book or article. For guidelines on how to appropriately attribute and cite an image, use the resources below.
From the University of Cincinnati, this website outlines image citation for each citation style (MLA, APA, etc.).
Scroll down to "Painting" to see examples of cited artwork in MLA style.
A research guide dedicated to visual literacy from UC Irvine, this page and its links provides some great information about copyright, attribution, and best practices for citing images.
From Simon Fraser University, this guide shares information on how to find and use images, including citation and attribution.
Try searching some of the following websites for images of your species. Most of these are government websites providing free images for educational purposes. Always check to make sure the image you use is in the public domain or licensed for educational use, and provide a citation for the source of the image.