My first post to the forum here. I have a design background but hardly any experience in programming.

int top;
int bottom;

void setup() {
size(700,700);
noStroke();
smooth();
background(255);
}

void draw() {
  
for (int i = 0; i < 600; i = i+100) {
  for (int j = 0; j < 600; j = j+100) {
    top = int(random(-25, 25));
    bottom = int(random(-20, 20));
    fill(int(random(0,255)),int(random(0,255)),int(random(0,255)));
    triangle(80+j-bottom, 120+i, 108+j, 65+top+i, 136+j+bottom, 120+i);
  }
}

noLoop();
}

So instead of random colours the fill is some kind of pattern. How are the patterns generated? Not sure. They're either generated or I make a library of tile-able images. Not sure the best route.