You have a really interesting design here, and I love the overall silhouette. Some advice specific to your questions:
-because it is a carrier, test out 2 heavy beam guns on the top and bottom, and fill the rest of the large turret slots with rapid fire cannons. then cover other small areas with anti missile turrets. the reasoning behind this: you should have a few guns to deal with frigate/large assault type ships (then again this is what your drones/fighters are fore), but you mainly need to watch out for the types of enemies that your fighters are vulnerable to: enemy fighters and mass missile spams.
-make sure to put a jump drive, anti-jump, lots of shields, a scanner, and lots of engines. (of course then power to run all this). other systems are obviously nice, but I think these are essential for a carrier.
-I would take some advanced armor out, in order to make the ship faster, and also to look better. your biggest defense for a carrier should be your fighters, turrets, and your jump drive. then shields. then armor. your fighters are really your armor. if you have enough to be effective, then your opponent will have to focus on them and not you. (of course i could be completely wrong... its all up to how you wish to dictate your fleets)
-to make the ship more interesting, I would, as I said, use what you have right now as a really awesome silhouette, and start carving out/tacking on large details. once you have that, then you etch in smaller things like pipes/slaps/strips/grills/general greebles.
-For hallways I just experiment with lights, struts, wedges, depth behind mesh, whatever I can think that follows my build style. a lot of the time what works is what follows your layout well.
If you are in a rut, work on another ship. do a lego replica, I can suggest many that would give you a challenge, then revisit this one and I assure you will be better and have a clearer mind.