What pictures are suitable for hanging on a wall more than 30 centimeters high?

The wall more than 30 cm high is suitable for hanging some small decorative paintings, such as watercolors, sketches, prints, photos and so on. The width of the hanging picture should be 0.8 times the width of the wall, and the height should be about 3/5 of the distance from the ground to the ceiling. The height of the center of the picture is equal to or slightly lower than the line of sight when people stand, so that the visual effect is the best.