Hotel elevator buttons should really not pose too much of a hassle for the designers; there is no need to be extra creative here: use the numeral 1 for the first floor, number 2 for the second and so and so forth. No other possibility should be considered. Unless of course, you are the designer of the new Jumeirah Saadiyat Hotel in Abu Dhabi and are aiming to have some fun at the expense of your guests.