why wont my cc CAS background not cover the whole screen

@ScribbleBaby   Hello!  I wonder if you have another mod/CC that is creating a conflict with the CAS Seashore background one.  If you do use other mods and CC, perhaps create a folder on your desktop (maybe call it Mods Temporary) and move all your mods/CC there, except for the Seashore CAS package file.  Also, delete the localthumbcache.package file located in the Documents / Electronic Arts / The Sims 4 folder before opening the game for testing.  Does the background appear properly in CAS without any other mods/CC?  If so, then you can start adding your other mods/CC back to your game Mods folder to see which causes the problem.

Just for some background, I initially thought maybe the Seashore CAS mod was broken.  However, I tested each one in my game and it's working for me.  So, this is why I think there may be a conflict with another mod/CC.  It is a lovely background so I hope you can get it working!

Here are some screengrabs showing how the mod looks in my game.

Seashore Day:

Seashore Morning:

Seashore  Sunset:

Edit:  Sorry for all the horse images.  I thought it would be fun to show them with a horse.. ;-)  Here is another image with a human sim showing the whole CAS background, the day version.