Hi Mary,
Node’s shape can be customized by using its CustomPathStyle property. The background of the Node’s Shape can be made transparent by applying the Transparent Brush to Fill Property of the Node’s CustomPathStyle. We have created the sample based on your requirement. Please refer to the sample from the attachment.
Please let us know if you have any further queries and we will be happy to help you out.
Regards,
Ramya
NodeBackground_1a5a1bd7.zip