Document.PreviewPicture Property (Visio)
Gets or sets the preview picture shown in the Open dialog box and when you click the File tab, and then click New. Read/write.
The PreviewPicture property returns and accepts only EMF files (enhanced metafiles). Microsoft Visio will raise an exception if the file you pass to PreviewPicture is a non-EMF file.
To delete an existing preview, set the PreviewPicture property to Nothing.
You can use the PreviewPicture property to include a preview picture in a template that does not have any diagrams stored in it.
COM provides a standard implementation of a picture object that has the IPictureDisp interface on top of the underlying system picture support. The IPictureDisp interface exposes a picture object's properties and is implemented in the stdole type library as a StdPicture object creatable within Microsoft Visual Basic. The stdole type library is automatically referenced from all Visual Basic for Applications (VBA) projects in Visio.
To get information about the StdPicture object that supports the IPictureDisp interface:
In the Code group on the Developer tab, click Visual Basic.
On the View menu, click Object Browser.
In the Project/Library list, click stdole.
Under Classes, examine the class named StdPicture.
For details about the IPictureDisp interface, see the Microsoft Platform SDK on MSDN, the Microsoft Developer Network.
Currently, only in-process solutions can use the PreviewPicture property because the IPictureDisp interface cannot be marshaled.