The templates are in the modinfo folder located in the model folder. They are named TIPicBack, VlPicBack, and Beautyshotback. These files will help you in determining the correct size of the new files that you create. Any new files that you create must match the size of those files. These files will also help in the placement of the image.
I use MS Photodraw and Taldrenmodviewer or the SFC2Edv2 editor to create mine.
I load the ships mod file in Taldrenmodviewer or the SFC2Edv2 editor and adjust the image of the ship to the size I want and the right angle (top of the ship).
Once the ship is at the right angle I use the Print screen <prt scr> key. This copies the image for the screen into the clipboard.
MS Photodraw will paste the image into a new picture.
From there it?s a simple matter of using Photodraw?s cutout tool (by shape and by color) to get image you want.
I open TIPicBack, VlPicBack, or Beautyshotback file into MS Photodraw and place the new image on top.
I readjust the image to fit into TIPicBack, VlPicBack, or Beautyshotback file and save it with a new name.
I am not sure if all graphic editors will work. There is probably several ways to create the files but you have to use what you have. I hope this give you a general ideal how to create the files.