You can edit the splash screens and title Screens from these locations.
C:\program files\ steam \ steamapps \ common \ GameGuru \ Files \ Languagebank \ english \ artwork ......For the main Splash Screen and Watermark
C:\program files\ steam \ steamapps \ common \ GameGuru \ Files \ titlesbank \ default.
For the loading screens
It must also be noted if you want to do this you must edit the screens "Before" you create your
standalone game so back the originals up first..
Or you can use a free third party tool called " StyleGuru " which makes the process much easier
https://forum.game-guru.com/thread/212352
Hope that helps
The only person ever to get all his work done by "Friday" was Robinson Crusoe..