thanks for starting this thread, it's a very important project and repositories such as
springerimages.com (which specifically allow searching for OA media) could be a goldmine of scientific content for commons.The Wellcome Trust in Britain is also running a pilot project (involving GLAM people) to study the best model for collaboration between scientific institutions producing large volumes of digital media and Commons, which sounds really exciting.
A concern I have with the mass upload idea is that being OA doesn't necessarily imply being available under a public license that allows reuse. A quick inspection at number of OA images from SpringerImages suggests that they can indeed be reused under a CC-BY, but I assume this is not necessarily the case in general, correct? The distinction between OA and CC-licensed contents is something we should keep in mind as part of our policy making effort within RCom.