@tuanphan thanks! the particles appeared now, it still is only a very tiny rectangle rather than a section background though... do you know if I can change this? I'm also trying to figure it out on my own...
Update: if i change the position tags to relative then the size is fixed. The main problem is that it acts like a standalone block rather than a section background, so the other text / content goes above or below it, never on top / overlayed...