I believe that has been done; we ship with VistaDB a provider for being an authentication provider but we don't ship a session state provider by ourselves.  That said I would not particularly recommend it and here's why:  Using a database as a session state server is an easy path to a performance problem because it can get hit *a lot*, and on each request.  It's also only needed when you have separate servers sharing state - which inevitably means using VistaDB on a network share were it is slower than on a local file system. 

I would recommend SQL Express in this situation - its 10GB limit just about has to be big enough for any conceivable session state scenario and it's free.