I realize that this began a year ago, but I must have missed it. Some of the highest grossing (no pun intended) indie horror films have very little blood. HALLOWEEN has very little. That held the indie record until BLAIR WITCH, surpassed it. Then came PARANORMAL ACTIVITY. Very little, if any blood in any of these indies.
People forget that horror encompasses a lot of subjects. Movies like THE OTHERS are just spooky, but have a nice twist. I grew up on the Universal classics, FRANKENSTEIN, THE WOLFMAN, THE INVISIBLE MAN, etc. Classic horror is more about suggestion. A creature attacks a person, but you might just see a shadow of it raising its arms and attacking. So much can be suggested through sound and shadows.