Visio does not natively support BPEL or BPMN, which are both commonly used in business process management applications. BPMN stands for "Business Process Modeling Notation" and is a proposed standardization for graphical notation for enterprise processes. The BPMN working community has come up with their own Visio stencils to use to create diagrams with BPMN 1.0 shapes: http://www.workflow-research.de/downloads/bpmn/
I haven't heard of anyone else in the BPEL community who has done a Visio template. If you have, feel free to post a comment.
--- Mai-lan