Both Unturned 3.x and 4.x should give players the ability to paint.
They should craft a canvas with a few pieces of leather and a couple sticks. Place it on the wall, press F on it and paint. They can choose between a few basic colors like blue, red, green, black, white, yellow, purple, and orange with 2 brushes, small and big only. Same with flags but flags have the extra mechanic to put texts on it as it already does.
I know kids will pain everything innappropriate, but I believe we’ve all seen that people don’t need paint to be innappropriate. So it won’t change much of the game, just a fun little addition
To be fair people already do that verbally with signs and notes. Though less of an impact.
Being able to draw or paint on objects and vehicles could open up a greater possibility of customization. I mean of course there’ll be dicks. It’s life! Someone will be driving around with a tank covered in dicks just for the laughs. But I honestly feel the pros outweigh the cons. Server owners can just make rules saying “No anti-semetic or sexually explicit drawings!” And everyone can go along on their way.
It’s a apocalyptic game, so more improv and uniqueness for player creations will usually always be a great addition. It’s their choice if they want to decorate their base with swastikas and penises. Some people wouldn’t like that of course, but again, it’s the apocalypse! You can just shoot them and take their stuff, maybe clean up their base and turn it into happy rainbows and sunshine.