NOA : Scientific Image Search. A project currently indexing 2.7 million free-to-use scientific images, extracted from CC-BY sources along with metadata and links. As you’d expect, ncbi.nlm.nih.gov dominates the URL links. I searched for European Lynx and had good results (big kitties), though nothing high-res.

The extracted images and their data are also being copied over to Wikimedia, where Google Images will pick them up after a while — and offer high-res filters.

Incidentally, ncbi.nlm.nih.gov has its own public and official Open-i Biomedical Image Search Engine. A search for European Lynx shows it is indeed strictly biomedical.