How far to you want to go?
It's kind of a shame that you have already painted and marked the turret before asking about adding details -- all this will have to be re-done if you add anything.
A couple quickies:
Add a vane sight to the commander's hatch.
Add a barrel clip to the commander's hatch.
Add periscope guards.
Fill the edge gap around the pistol port and blend it into the turret.
Add foundry marks (they might be there, but I can't see them).
Add .50 cal. stowage brackets to the rear of the turret.
If you don't have the welded-on armor plate on the gunner's side, add it or add the cast-in bulge.
That's enough to keep you busy for an evening or two ...