For the instance scenegraph location, in addition to the standard Katana instance attributes and arbitrary user data (geometry.arbitrary.*), KtoA recognizes the following extra attribute:

 

Also, for arbitrary user data, you may set arbitrary data that has any scope (primitive - Arnold constant, point - Arnold varying, face - Arnold uniform, or vertex - Arnold indexed).  KtoA will pass that along to Arnold, which if it matches the instance source in topology (e.g. the number of varying values is the same as the number of vertices in the source mesh) the user data will apply to the instance at render time.  Finally, because instance source locations can have various children of varying topologies, if you wish to override or add arbitrary data to a particular instance source child location when it is instanced, you should create a child of the instance location (child of location type locator will do) and set the geometry.arbitrary.* data there.  If the instance child matches an instance source child by name/path, it will then apply.

For convenience, instancing can be set up more easily using the ArnoldInstanceSettings node.