Here is a tutorial to make a CG Gallery without using flags. 

Note: This doesn’t feature an unlockable feature, rather, it has every CG for the game in the library as a button with a ‘no-spoiler’ blur. Perfect for games that only have a few CGs.

Things you’ll need:

• Preview CG (blurred image) resized as a Button
• CG Gallery Backdrop Image (Recommended, but I don't have one in this tutorial)
• A Close Button

ONE: 

Create a screen called CG GALLERY. 
Add the Close button in a corner in the Open Page. Then add the CG Button wherever you’d like.
 





TWO: 

Create a screen for each of your CGs. 
Add the Close Button and Show CG Image. 


THREE:
Add actions to your buttons: Close Button in Gallery Screen should close the Gallery, Close Button in CG Screen should close CG 01 (or however many you have). 

FOUR:
You can test out your work in a test scene or more likely, in the main menu by adding a ‘CG’ Button whose action opens CG Gallery Screen.
After opening the specific CG, you will back out of each CG Screen and the Gallery Screen back into the Scene/Main Menu.  






That's it! 

Nice! Thanks for making this @Neeka, I'm sure many people will find this super helpful!