Thanks Oshyan.
The only copyright I found on the above site is - Diamond Fire GlassĀ® is a Registerd Trademark with the United States Patent and Trademark Offices. The pictures themselves have no copyright and this quote from Wikipedia seems to keep the use of these under safe practice - "For example, the copyright which subsists in relation to a Mickey Mouse cartoon prohibits unauthorized parties from distributing copies of the cartoon or creating derivative works which copy or mimic Disney's particular anthropomorphic mouse, but does not prohibit the creation of artistic works about anthropomorphic mice in general, so long as they are sufficiently different to not be deemed imitative of the original..."
I might be safe to use these as textures, especially since the site is about their end product - jewels. Nevertheless, I won't know unless they make it clearer.