A little while ago, Niall Ginsbourg posted an introduction and some screenshots for a new version of Big Screen Photos that he is developing using Media Center Markup Language (MCML). Yesterday, he published a much more in-depth post describing the features of Big Screen Photos version 2, and he also invited anyone interested to email him to get an invitation to the private beta.
You can view his blog post at http://mobilewares.spaces.live.com/Blog/cns!78533A1A2E078194!425.entry.
I got a beta invitation yesterday and have been trying out the application over the past day or so. I'm really impressed with what Niall has been able to do with MCML and the tools/documentation in the Media Center SDK. If you have a chance, I encourage you to check out this blog post and contact Niall if you would like to try out a beta version of the application on your Windows Vista Media Center system as well.