This example has some effective step to teach you a cracked wall effect without any doubt, follow some steps to make this effect.
Take a picture: Start this example with a wall picture.
Selection: Make selection by the Polygonal lasso tool (L key) on the wall as I have done here.
Layer style: Go to Layer menu > Layer style > Drop shadow and use same settings as given below.
You will have this picture.
Layer style: Now change layer style.
This is the result.
Recommend the tutorial