This area may need some tweaking
ATM if the skin fails to match up any conditions then "Digital Video" shows up normally if item is a folder or top level of a Set.
If you don't have "Use Disk Cases" enabled - found in the left menu of some views Then skin checks if list being shown belong to TVshow then shows "TV Series" If not TVShow then checks the file extension and tries to appropriate case eg AVI, MKV etc falling back to Digital Video if skin does not have the correct case.
If you do have "Use Disk Cases" enabled then skin checks the following in this order and uses the first match.
N.B. the "Use Disk Cases" is global and will change all views.
1. In the Path to file or in file name the words 'bluray','bdrip','bd25' or 'bd50' - then use bluray case
2. The Path or Filename of file contains '.3D.' or '.SBS.' then use 3D case
3. Checks for 'hddvd' in file name or path, if found use HD-DVD case
4. Check for 'dvd' in file or path = Use DVD Case
5. Check name and path for 'pdtv','hdtv','dsr' - if found use TVSeries
6. Nothing matched now use Digital Video Case
So in short if
.3D. found in name then use 3D Case, but if you want I'm quite happy to add
.3DBD. into the mix for the case to show.