[tiermann]

Subsplash is not the startup animation. Startup animation isn't changeable through buildOS yet, but I made a quick solution...

-Download the attached zip.
-Extract to your USER_OEM folder
-Rename your animated gif to MyAnimation.gif and replace the one in the MyStartupAnimation OEM.
-File->refresh in buildOS if it's open.
-"My Startup Animation" should now appear in the Boot Options section.
-Select it. (Startup Animation should select automatically)

The attached OEM already contains the stock Sprint animation so you can skip the replacement step if you want to use that one.

Notes:
It will still play the default animation on the very first boot. Every boot after will be your custom animation.
I did it this way to avoid buildOS asking if you want to replace the file every time you build. If you don't care, delete MyAnimation.gif and initflashfiles.txt from the OEM and just add a WMStartup_ani.gif.

Edit: Fixed. Please Re-Download