So in an effort to eliminate these kinds of errors, I am going through all the image files and replacing them with the recommended formats.
It is a long process and I am just starting. One good side effect is that I am saving disk space in the process, as well as eliminating a bunch of unused functions in the game script. So by the end of this process I think Star Explorers will become a much tighter program that takes up much less room on your hard drive.
In the process I was able to identify some textures that were missing from the game files. However, I am guessing I will mess up in the process and some textures might be missing (if I failed to reference the right file or something).
Changed depots in testing branch