Colon after exclamation mark for subtitle or not?

There are really no rules as far as advertising and movie titles go. But I think a colon after an exclamation point would look dumb. This may be on reason they didn't put an exclamation point at the end!

Never a colon after an exclamation mark, definitely not.

I would write that title as: "Star Wars - The Force Awakens!". Many people in the movie industry do like to use exclamation marks! The use of an exclamation mark in the middle of a title might seem strange to me.

Note that I am a 70-year-old Briton. Many modern forms of expression do sometimes seem strange to me.

No exclamation mark -- it signifies the end of the idea.
So, it would be more like:

StarWars!
The Force Awakens.

No. No colon.

The exclamation goes at the end; if there is a subtitle, the end does not occur until the subtitle is complete:
Star Wars: The Force Awakens!

In your example, no colon.