Not much shore terrain is made in this scale.
Check the ex-Hallmark Thoroughbred range at Magister Militum. There is a Trekroner Fort (from the 1801 naval attack on Copenhagen), Martello towers, and a Vauban fort. I actually cut up the Vauban fort wall sections and made a few different shapes of Vauban walls to fit around towns.
Some of the 2mm buildings and towns and farms in the Irregular 2mm scenery range are sufficiently small to fit into 1/2400 scenery.
Navwar makes some 1/3000 dockside buildings, wharfs, a graving dock, and a few other misc items.
Some of the shore batteries made by War Times Journal will work as shore batteries in the ACW. You can double the number available in this range by buying each one in both 1/3000 and 1/2400 and using them as "small" and "large" batteries. :-)
Valiant makes a "star fort" model which is actually three identical pieces that fit together along triangular sides. It's a bit overscale (1/2000), pretty stylized and not very ACW, but kinda charming.
As always, check Shapeways. Maybe somebody has made something that will work. Sometimes things in the wrong scale can be rescaled smaller or larger, if you contact the creator.
Links to a lot of these here.
- Ix