We're currently working on a grant proposal that is related to the usability for uploading and embedding media files to Wikimedia Commons. (This is an area that we will likely not be able to address in detail as part of the Stanton project, so we're trying to parcel it into a separate project.) As part of this proposal, I would like to make a compelling case that pictures and other media uploaded to Commons benefit from strongly from the increased visibility, especially through Wikipedia articles. I'd also like to demonstrate that images get used in multiple languages and multiple projects.
The simplest research approach that any volunteer could take is to take a sample (say 50 featured media and 50 random ones) and to catalog in a spreadsheet usage across Wikimedia projects, using the CheckUsage tool. But I'm sure there are other approaches - both quantitative and qualitative - that might work as well, e.g. based on Wikipedia article traffic statistics.
I'd love to see some volunteer input into this question, which essentially boils down: Why is Wikimedia Commons awesome, and why is it worth investing in to make it even better? I've started a page on Meta here if you want to contribute ideas on-wiki:
http://commons.wikimedia.org/wiki/Commons:Case_for_Commons
But feel free to e-mail me off-list as well. :-)
Thanks for any and all help, Erik