At the article that LTS linked, I'm offended (boo hoo) that while they identified the poet, they omitted credit to the painter.

This mermaid is well known:

The Artist:
John William Waterhouse
England
Victorian Romanticism
b.1849 - d.1917

A brief bio, and the first 10 of 90 of his paintings at the site can be found at the link.

The painting:
A Mermaid
1901, Oil on canvas,
38.58 x 26.38 inches / 98 x 67 cm
The Royal Academy of Arts,
London, England

Appears in a very good quality image (for a web collection) at Page 2 (at the bottom of the page) at the above site. Click the thumbnail to open a larger version in a new window.

He's not actually one of my "most favorite" artists, but deserves to be credited - especially [IMO] when his works are used for commercial purposes.

John