DVD Extras

Sucker Punch: Behind the Soundtrack

and

Sucker Punch: Animated Shorts
Feudal Warriors
The Trenches
Dragon
Distant Planet

Aside from a Maximum Movie Mode*, these are the only extras on the Sucker Punch Blu-ray, and they run under three minutes each. The first is a brief (obviously) look at the film's intriguing soundtrack. It's clearly designed to be promotional, but incidentally reveals a few interesting tidbits. (An even shorter version of it is linked to above.)

The animated shorts are 'prequels' that detail the background to the fantasy worlds visited in the film. It's the kind of thing you know can't be that essential because otherwise it'd be in the film itself -- The Trenches doesn't have much to do, for instance, because that world is explained in the movie -- but a couple of them are quite good anyway. Distant Planet in particular, as that felt one of the more under-explained environments to me. (All can be watched in full at the above links.)

* which, in fairness, could be very good -- it's potentially a feature-length making-of/commentary, after all.