---Update---
you will find the six new loading screens in the "update loading screen files" folder

Installation:
open openiv and enable edit mode (better backup your files before doing any changes)

Replace all files except LoadingScreen_Startup.ytd in the following folder:
GTAV\MODS\UPDATE\UPDATE.RPF\x64\DATA\CDIMAGES\SCALEFORM_PLATFORM_PC.RPF

Replace the LoadingScreen_Startup.ytd file in the following folder:-

GTAV\MODS\UPDATE\UPDATE.RPF\x64\DATA\CDIMAGES\SCALEFORM_FRONTEND.RPF

And enjoy : o )