Mythic has released some information about the keeps in New Frontiers, the upcoming free RvR expansion for Dark Age of Camelot. An excerpt to get you started:
In the original frontier zones, each frontier Keep looked the same across each Realm - each Realm had their own outpost design and all seven shared this same configuration. Now, in New Frontiers, each frontier outpost has a different layout. There are seven different configurations - each Realm has one of each type. These keeps will be designed to have different strategic elements - different strategies will have to be employed to successfully siege each different keep design. In general, each outpost will have wall sections, towers, a door, and an internal fortified keep.
Each section of a keep will have hookpoints that can be utilized by any member of the owning realm. Players will be able to attach siege weapons, NPC merchants, and NPC guards to these hookpoints. A player or group of players can go to a tower or section of wall and show which hookpoints are available for use. The player can then choose to build a siege weapon and fire it, buy additional NPCs or upgrade existing NPCs tied to that piece.
When you upgrade a keep in New Frontiers, you will visually see the geometry of the keep change. The footprint is not affected, but upgrading will result in taller towers, taller walls, and more hookpoints for siege weapons and NPCs.