The Association of Equipment Manufacturers has an online pictorial database. I see it as an illustrated guide to 130 ways you can get hurt, killed or worse by evil machines.

This database was developed to assist designers and technical illustrators in communicating effective safety messages through the use of consistent “industry-recognized” pictorial representations. Development of the database is guided by industry professionals and will be expanded as more product and process-specific pictorials are identified.

Available as .eps or .dxf files. Or grab a large version of the index I created above.