The National Center for Biotechnology Information (NCBI), a division of the National Library of Medicine (NLM) at the National Institutes of Health (NIH), has developed and will maintain the newly-announced Images, a database of 2.5 million images and figures from medical and life sciences journals. The new site is available at http://www.ncbi.nlm.nih.gov/images.
From the front page you can browse recently-added or most-cited literature, but you also have the option to do a simple search by keyword (an advanced search builder allows you to search through several different fields.) I did a search for autism and got 1580 results, mostly charts. (“Fig. 4. From: Automated vocal analysis of naturalistic recordings from children with autism, language delay, and typical development.”) The search results have a thumbnail, paper title, and a brief amount of context; there are also links to a citation/abstract for the article as well as full text.
This is not a fuzzy-wuzzy biology search engine; the vast majority of the results I saw were data charts. Try doing multiple keyword searches for concepts which you’re trying to relate; the first result for thyroid diabetes found me a very interesting Venn diagram.