Since Canon not even bothers to provide a 64 Bit aware codec for CR2 format as far as I know, the only chance to get that format supported at all would be software from other providers, i.e. Fast Image Viewer. But even with that viewer installed I doubt,
that there is a chance to integrate the functionality in Vail. On client side Media Center in Windows 7 is capable to show CR2 images, if an appropriate codec is installed.
For remote viewers the size of CR2 would be overhelming for the bandwidth given in most scenarios, therefore a local conversion on server side would be the only method to allow viewing in a quick manner. I agree this is a feature on my wishlist as well,
since I store the most of my pictures in that format.
Best greetings from Germany
Olaf