Relative image files not found. Background render. No error, just magenta textures Another one of these problems...

Renders fine on Windows desktop, but not on headless Linux box.  Image files are in the same dir as the blend file, like on the desktop.  Using relative paths.  CLI output shows it's loading image files, but gives no error as it probably should since the I get the magenta textures.

Using identical blender versions btw desktop and Linux, v2.76.

Using --debug-all is no help.

Command:
blender -b --debug-all -noaudio internet3.blend -s 1069 -e 1069 -a

Any suggestions?

Edit: The strange thing is, a referenced movie file IS successfully found and included in the render even though the images are not.
Got it.  The clue was that another asset, a movie, was found and rendered, but it was in a subdir instead of being the the same dir as the blend file.  So, I moved the images from the same dir as the blend file to their own images subdir.  Then, open the blend file and select File > External Data > Make all files relative.  Save.