Graphics network sharing & location

I have a ginormous graphics pack that I want to let my subsite members have access to for spiffing up their sites. (arrows/bullets etc etc)

any suggestions or guidelines on how to manage and where to put that? is there any way to control accessing files like that?

I'm running WP3.5.1 multisite subdomains.

seems like the media library is not the right place to share image files across the network -- but if I put graphic files in /wp-content/images/graphics/ how would admins know what is available? security?