Добавил заглушки

DemoExam/DemoExam.csproj

@@ -191,6 +191,7 @@
   </ItemGroup>
   <ItemGroup />
   <ItemGroup>
+    <Resource Include="images\picture.png" />
     <Resource Include="images\logo.ico" />
     <Resource Include="images\logo.png" />
     <Content Include="Model\Model.Context.tt">

DemoExam/Model/PAgent.cs

@@ -37,6 +37,10 @@ namespace DemoExam.Model
             get
             {
                 string pathImage = Environment.CurrentDirectory + Logo;
+                if (Logo == null)
+                {
+                    pathImage = Environment.CurrentDirectory + @"\images\picture.png";
+                }
                 return pathImage;
             }
         }