At first glance it's awesome and I have no complaints. However, since you're looking for some sort of fault, I have two ideas, neither of them a matter of aesthetics.
Problem 1: non-weapon functions
You've got a nice set of engines there, and what is either a Star Destroyer-style command bridge or a nav/comm/scan mast with an observation window. I don't know if you've got anything on the ventral side, but additional sensors in the blind spots couldn't hurt. All those turrets probably have their own targeting sensors, but wide-area scanning tends to be a different beast. Speaking of targeting sensors, the side-mounted objects you mentioned that look like small forward cannons could be remodeled to remove the cutouts and maybe add some other detail to make them targeting sensors for the spinal armament.
You mentioned a shuttle bay, that would be good. Also, there are a few places that might be docking ports, but that's not clear without textures. There's also plenty of odd little extras you could add by considering famous sci-fi ships. There's the garbage chute and minelayers on the Imperial Star Destroyer, various radiators and vents on all sorts of ships, escape pods, etc.
Problem 2: Turret placement
It looks like you have 3 models, which I will call primary, secondary, and point-defense turrets. Exactly how much the point-defense matters is going to depend heavily on whether the primary or secondary turrets are defensive flak or anti-ship weapons, but it still couldn't hurt to move some of the PD guns to better locations (or add a few extra). The forward dorsal pair have a rather poor field of view due to the forward dorsal primary turret. There doesn't appear to be any coverage forward (as you mentioned), aft, or around the bridge.
As to the primary turrets, something that size should require a certain amount of space underneath for power cables, ammunition or coolant if any, rotation mechanics, and at least some basic structural bracing. That is, placing two turrets on opposite sides of a protrusion that's smaller than either of them looks a little hard to believe. The Nova-class dreadnought from Babylon 5 is probably the most egregious example in mainstream sci-fi.