I agree about the sinks....I have 3 - one large deep industrial sink with a trap (which I do not clean) and 2 regular kitchen type sinks....
I also agree about the storage....the more the better! Cubby holes for storing still life object, skinny drawers for samples, etc.....do you do portfolios with the students? Do they need to keep those somewhere?
What about large drying racks? Somewhere/somehow to hang things to dry?
Something else that I would LOVE, but can't get in this school because we have old high cement ceilings.....a newer school in our area added retractable extention cords in the drop ceiling of the art room...I think they had 8 of them which could be pulled down so that students could use hot glue guns, etc. without having cords all over the floor, and when they were finished they were retracted back up into the ceiling (yes, about 2 feet of the cord dangled from the ceiling above the height of most people, but that's better than cords on the floor). I just thought that it was a brilliant idea!