Experts are currently collecting over 10,000 inscriptions that have no one has translated in over 500 years since Ferdinand and Isabel evicted the Moors from their mighty fortress. Using the high-tech gear, they've managed to translate about half, and have compiled over 3,000 in a DVD. I've been all over the Alhambra myself and I can;t imagine how painstaking the catalog process must be on those vaulted cathedral ceilings.
So far the inscriptions are mostly the Nasrid motto: "There is no victor but Allah." But in accordance with that particularly fruitful time in Arabic culture, there are many other things written on the walls, from poetry to aphorisms, such as "Be sparing with words and you will go in peace."