1.  Take a screenshot of the item in Surveyor.
2.  Convert it to a 240 by 180 pixel jpg file using PSP8 or any other program that can do the same.
3.  Copy that image to the items folder in Trainz.
4.  In the config file add:
 
thumbnails
{
     0
     {
          image     itemname.jpg
          width     240
          height    180
     }
}      
 
5.  Use a copy of the image when you make the CDP.
 
Ben