Hi David,
My apologies for the delay in responding to you.
I was not able to reproduce the issue you have mentioned here. The GDI+ error occurs when HttpHandlers are not included in the Web.Config file.
Could you please check whether the below HttpHandler is present in the Web.Config file of the deployed setup.
Also please refer the documentation which dicusses about the deployment with Syncfusion Products:
http://www2.syncfusion.com/library/ [ Essential Studio/Getting Started/Deploying Essential Studio for ASP.NET]
Thanks,
Ramya