Well, you asked what more to add? There are doors, hatches, vents and ventilators, basically everything that makes a modern steamship function! You've got very little of all that. You're right, your drawing does look plain, but, while we can advise you and direct you to modes that you can study, we certainly cannot and will not do the job for you - afterall, it's your ship, your creation!
Let me ask you, what's that weird looking raised structure that goes across the forward section of your superstructure, it's not even tall enough to fit a normal-sized man, and it slopes oddly down towards the front of the bridge complex? That looks very redundant to me. Your funnels may also need some work. Right now it appears as if the second one is also a redundant, even a non-functional one, and gives the whole vessel a strange imbalance. You can use two, heck, even three funnels, but they should be in somewhat congruence with eachother to appear realistic and believable. The 40 mm Bofors you've put right atop (as it appears) of your second (elevated) 5"/38, and I know it's not literally on top of that turret! - you could better move either slightly forwardor aft, to clear the turret entirely.
Also, my friend, you need boats! There's a suitable USN boat sheet in the parts section. Again, consider the function of yor ship and equip it accordingly. If it's a flagship, it'll in all likelihood carry one or to extra motor boats, steam cutters and/or pinnaces.
As for the bridge, it's much better than when you originally posted your first attempt, but the levels still lacks any kind of sophistication, such as dedicated bridge wings, mooring stations, signal stations etc. Again, you'll be inspired by looking at the relevant USN drawings - and, for that matter, other nations' ships as well!
It's definitely an improvement, but can still use quite a lot of careful TLC!
My Avatar:Петр Алексеевич Безобразов (Petr Alekseevich Bezobrazov), Вице-адмирал , царская ВМФ России(1845-1906) - I sign my drawings as Ari Saarinen