Problem adding a custom Loading Gif | Minecraft 1.12.2 Forge-14.23.5.2854

Dear Forge Devs,

I am sorry for posting an issue on an ancient MC version, but Google couldn't help me. 

I have been trying to get a custom (somewhat custom at least) Forge loading screen on my modpack so I tried on my testing 1.12.2 Forge build which only has Custom Main Menu and ResourceLoader installed. After editing the splash.properties file to get the colors I want (which works fine) I wanted to get a custom loading gif like in ATM3. I've created a .gif image in gimp which might be the problem. I uploaded it to giphy just in case. I renamed it clouds.gif just like ATM3 does in their file but when loading up minecraft I get a black screen and a crash shortly after. It shouldn't be because of my specs, they are sufficient. Crash report says it is because of a splash file issue. This is the full crash report.

Thanks in advance.

P.S: Quick Side Question, is it possible to use custom textures for a background in the splash.properties file?