Just a few words of caution... remember that essential oils and aromatherapy oils should be diluted in a carrier oil (olive, almond, jojoba, vit e). And having a scent free carrier oil is great if (like me) you suddenly decide during the birth that a formerly wonderful scent is now horrible and you can't stand it! Also, keep in mind that some oils can interact with some medical procedures, so let people know what you're using if interventions become necessary and remember that carrier oil/essential oils applied to the mama's belly/chest may be too much for a brand new babe!
A hot sock with EO or herbal blend inside, a cloth with EO, EO in carrier oil, a water bottle spritz with EO mixed in, little bags of different "potpourrie" or even baggies with differently scented candles (not to burn, just to smell), are all ways to scent the room. Keep in mind most hospitals will not allow things like candles or incense, and many birth centers limit what can be used as well. Ask ahead of time...
That said, there are a few I always pack (as a mama and as a doula when I was doing that):
--lavender for relaxation (I use this during my meditation and hypnobabies sessions to create a stronger association with the scent)
--clary sage also for relaxation
--rose as a general "support for feminine energy" as well as for it's uterine tonic aspect
--peppermint for tummy qualms and increased focus
--geranium to lift mood and improve circulation
--ginger for circulation and warming (in case you get the shivers, especially nice as a foot rub IMO)
And Bach rememdies:
--Rescue Remedy since it's a great all in one blend (I like both the drops and the cream)
--Aspen for fear of the unknown
--Mimulus for fear of the known
--Olive for exhaustion
--Rock Rose for emergencies (really good for an unplanned c/s or other birth trauma)
Homeopathics:
--Arnica for all sorts of physical birth trauma
--Aconite for any emotional shock or trauma
--Sepia for emotional numbness or exhaustion
And honey infused with comfrey for any tears (or bruising/injury elsewhere, say at an IV site after the IV is removed). Pure aloe gel is also nice on tears, but he honey/comfrey blend rocks! (says the mama who had a 4th degree tear with dd2 and got to try a few too many healing creams)