This happens when the game is set up with a shipset being used by an empire that is not in the mod. You most likely selected a shipset that is not in TDM to use. To fix the problem:
1) Navigate to TDM-Modpack\Pictures\Races
2) Create an empty folder that is named the same as the shipset you are using.
This will cause that shipset to be available for use in the TDM mod. Since there are no files in the folder, SE4 will look for the same folder in the default Pictures\Races folder, and will load all the relevant files.
This thread is for SE5 suggestions though, so please create a new thread to ask more questions in the future.
