I haven't roleplayed a Gnome Priest before, but there are a couple of items I'd look out for:Gnomeregan Bonechopper
Would be a suggestion of mine, but Priests can't wield swords, and there isn't a weapon with this skin labelled as a "Dagger" I'm afraid, so you're a bit out of luck there. :( There's plenty of Maces you could grab, on the other hand, that would be perfect if you need to administer a quick a "anesthetic" to a patient. Watch out for spikes though!
Next up are a pair of gloves. These are Bloody Surgeon's Mitts
and they look great for anyone going for a "Doctor" like role. They drop from Broggok in the Blood Furnace with a fairly good droprate and they look awesome. Very simplistic, but a great touch.
As for headgear, we all know medicine can be messy business, and we can't have you coughing near an open wound - it might get a nasty infection in it! You're going to need something to cover that gob of yours. So, when it comes to a face-mask (if you want to wear one over a pair of goggles - at the end of the day I'd say it's your call - or you can keep both for different occasions), you can pick up White Bandit Mask
from any good tailor, or if you're more partial to the green of surgery gear there's always Venomshroud Mask
which is a random drop from a lot of mobs, especially in Tanaris. There's also a lot of those new veil's floating around from quest chains. For example, Demonkiller Mask
As for clothing, I don't know if you'll want to go with a robe or a combination of trousers/shirt, but hopefully those suggestions are somewhat useful.