The vector stencils library "Choreographies" contains 28 symbols of choreography tasks, collapsed and expanded choreography sub-processes for drawing business process diagrams (BPMN 2.0).
"Choreography – Tasks performed by
participants and how participants
coordinate interactions via messages. ...
(1) Sequence of interactions between Participants.
(2) Choreographies exist outside of or in between Pools.
(3) A Choreography Task is an atomic Activity in a Choreography Process.
(4) The task represents an Interaction, which is one or two Message exchanges between two Participants.
(5) Helps to show who initiates the activity and the first message." [omg.org/news/meetings/workshops/SOA-HC/presentations-2011/14_MT-2_Brookshier.pdf]
The shapes example "Design elements - Choreographies BPMN 2.0" is included in the Business Process Model and Notation solution from the Business Processes area of ConceptDraw Solution Park.