Sanjaya, it seems Tristan has not been using SCN lately, but you might want to ask your SAP account representative about the promotional materials or contact the local SAP office.
I don't recall any SAP posters at our implementations, but we had some corporate stuff printed with our own project name. We also had an employee contest for the best project name, which was lots of fun.
You can also find some unofficial posters here, for example. 