I'm proposing to add "Film score" to the work type list.

Film score as a term doesn't only cover orchestral scores for symphony orchestra, it covers any type of music composed for a film. Wikipedia page about film scores: http://en.wikipedia.org/wiki/Film_score

Some example film score works in MusicBrainz:

Jerry Goldsmith / Congo: http://musicbrainz.org/work/97b36f87-3997-410f-b087-fbbb43b8b039
John Williams / War Horse : http://musicbrainz.org/work/640cdba7-f86c-4e12-968b-251c793eae8f
John Williams / Adventures of Tintin: http://musicbrainz.org/work/059bbece-42e7-4300-837e-c56d69ef8604

I personally wouldn't use this type for the parts of a film score (often same than track titles) but only to works presenting the full film score.