Spatial data? There's no relation between spatial data types (geometry and geography) and database snapshots.
No, there's no way to create the database equivalent of VM's differencing disks. Restore the users each a copy, let them do as they like with the copy, delete and recreate it as needed.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability