For you guys with tattoos, in my opinion its best to be honest, they WILL see them once you get to Dubai in the medical and imagine the embarassment of getting sent home. I have 2 tattoos one rather large and i too was not sure wether to admit it but i was honest and here i am in Dubai. For males its not so much of a problem as you wear a white t-shirt under uniform, for females its probably more of an issue, the shirts are pretty see through and although you have jackets and service waist coats, there will be times when the pursers want the crew to board with jackets off and thats when they will be seen !