If you are looking for mermaid art and clip art, Mermaids and Other Inhabitants of the Deep (Dover Electronic Clip Art) (CD-ROM and Book) is the best option for selection and cost. Jeff Menges did a wonderful job as always compiling the images and this is like having a mini art book devoted to mermaids. Some of my favorites are provided.
Product description from the publisher:
Nearly 150 beguiling images — dozens of them in full color — feature Rhine maidens and sea fairies as well as scores of winsome mermaids. Sources for this unique collection include Victorian and Pre-Raphaelite art, images from the Golden Age of Illustration, and stories such as Hans Christian Andersen’s The Little Mermaid, Friedrich de la Motte Fouqué's Undine, and Wagner's Ring cycle.
Image File Information:
Includes 147 royalty-free images—38 full-color images saved in JPEG format and 109 black-and-white images saved in TIFF and JPEG formats.