Amazing place to go!
There are a few shops but I brought my film home for developing so I don't know about the service there.
Definitely take the ferry to Gozo and see the Grotto! Valetta, Sliema, Marsaxlokk, St, Thomas Bay, St. Julien's, definitely Mdina for the panoramic views, the Dingli Cliffs on the western coast, also the Blue Grotto near Zurrieq is amazing when the waves a big, the catacombes, the neoliths, I could go on and on. Watch in the evenings for fireworks, there are so many different religious events that each small town has it's own displays. See here. Everywhere you look there's a photo.
I spent two amazing weeks there. The bus service is very good and will take you to every major spot. Renting a scooter is highly recommended if you want to explore. You could spend quite a bit of time on Valetta alone but see the country side.