https://www.tamriel-rebuilt.org/galleries/house-dres-concepts

Already in Data, already in use in TR.

The set has DE identifiers, its appearance is muted and somewhat neutral, not impressive but it can fill a niche.

A small expansion to the exterior stronghold tileset. It includes two towers, a balcony mesh and some rubble and ruined variations of vanilla pieces.

http://mw.modhistory.com/download-55-10305

The exHlaalu tileset has reuse permissions (attribution required) if all mesh IDs are changed.
Since we'de be using this highly modular tileset with new IDs (and CS IDs) anyway, this should not be a problem. What needs to be done is that someone needs to change the 105 exHl_org meshes into fitting IDs and upload that.