I'm not qualified to give much advice, but... seriously, don't. Hornets build their nests very fast:
<http://bhaskism.tumblr.com/post/786655912/hornets-nest-in-my-room-not-only-are-these>
....
Attentive readers of my LBOTalk oeuvre will recall that this topic is close to my heart.
In fact, of my three top interests in life, the life cycle, configuration and behaviors of Vespa crabro ranks rather high (the other two being: tireless advocacy for the pencil skirt/stilettos combo and um, social justice).
Each Spring, I reconnoiter the grounds and examine the house's exterior, looking for signs of honey bee, hornet, yellow jacket, paper wasp and other neurotoxin delivering beastie activity.
Will it be the spear of war or an inter-species entente cordiale? Several factors determine the Summer's course towards either belligerency or coexistence. I prefer coexistence; these animals are rather beautiful and, when safely viewed, their activities are fascinating to study. Plus, they do their part to keep the population of competing creatures down. A reoccurring black and white hornet nest in my massive oak tree solved our once yearly yellow jacket problem -- I think the b&w's wage war early on the jackets, wiping out vulnerable, Spring stage nests And since the b&w's, for all their fearsomeness when protecting their nest, are fairly chill while away from it if left alone, I prefer them to the more skittish yellow jackets (who really become agitated in late Summer/early Fall as the queen, prepping for overwinter, cuts off worker nectar supply).
Of course, excessive proximity is a vote for war. A hornet nest in your bedroom is about the strongest provocation imaginable.
The trick with an indoor situation is to choose the right weapon(s). My favorite is liquid Sevin insecticide. Sevin's most potent ingredient from a wasp/hornet killing POV is Carbaryl. Unfortunately, Sevin (which is also sold in a dust formulation -- in fact, the "liquid" is really Carbaryl mixed in water) is far too toxic to use indoors. Many would argue that it's too toxic to use period (honeybees are devastated by Sevin - which is undesirable, to say the least).
An alternative is to use one of the aerosol delivery systems (for example, from Spectracide, Ortho or Raid). The advantage is that these are designed to spray a stream between 15 and 20 ft away from the nest, giving you a chance to kill without being in the immediate line of counter-attack.
But again, the problem in an indoor situation is the extreme (and I mean, extreme) toxicity of these products. If you got Malathion (one of the typical ingredients) all over your bed your best bet would be to destroy it.
Since the nest is still in the building stage (though, from the pic, rapidly nearing completion!) a professional might opt to gear up in a bee outfit or Tyvek suit and use a powerful shop vac with insecticide dust in the containment vessel. The advantage is removal with a minimum amount of poison spread about your living space.
I know far too much about this.
Good luck!
.d.