Hi Dann, it actually wouldn't be that hard to modify the AnimatedGIFs sketch to use internal flash. In the latest version of the sketch (more recent than what's included in the SmartMatrix Library Examples), I made the file functions generic so you can use a different FAT library. You could adjust that code to read from internal flash instead. The code you need to change is mostly in FilenameFunctions.c:
fileReadBlockCallback() would need to load bytes from internal flash into the buffer instead of calling a function in a FAT library.
I'm not sure the best way to load a GIF into internal flash. You could probably just do what you did for a bitmap. The Teensy Audio Library I believe has some utilities that load .wav and other files into internal flash and you could look at that as well for another example.
If you want to take this on, please post back if you need more help or get something working.