A nightlight is a good idea in an inside cabin, or in any cabin if you tend to get up and use the bathroom in the middle of the night - put the light in the bathroom to help you find the door.
Celebrity does have hairdryers in all cabins, in the bathroom. I've heard they're not very strong, but I wouldn't know since I don't have much hair...
Celebrity has an automated wake-up call service so the phone can be your alarm clock. Also, if you order room service they'll call your cabin before they get there, waking you up and giving you a few minutes to get up and put on a robe.
I always bring some Woolite packets on a cruise in order to wash out clothes in the sink - gym clothes, swimsuits.
Hope this helps!