DeviantArt.

[sealforvr]

For great merfolk images and ideas, DeviantArt is a great resource. Top artists around the world post here as a kind of digital portfolio that is searchable.

http://www.deviantart.com/

Below is just one example of what you can find. I've used them not only professionally as a graphic designer but also for costume ideas.

41098

[AniaR]

I have been on deviantart for 14 years :) I run a group called deviantARTmermaids and there's load of mermaid art on it.

[sealforvr]

OK, Cool, I'll look you up!