Does this work for you?
Sub RemoveOrgChartPictures()
  Dim vsoPage As Visio.Page
  Dim vsoShape As Visio.Shape
  ' Loop through all pages in the document
  For Each vsoPage In ThisDocument.Pages
    ' Loop through all shapes on the current page
    For Each vsoShape In vsoPage.Shapes
      ' Check if the shape is an org chart shape (adjust this condition as needed)
      If vsoShape.Master.Name Like "*Org Chart*" Then
        ' Remove the picture from the shape
        vsoShape.Fill.Solid
      End If
    Next vsoShape
  Next vsoPage
End Sub