Auto Repairman Witnesses

Damages Witnesses can include the auto body repairman who worked on your car after the accident.
In addition to pictures, have him measure and allow you to photograph the distance the hydraulic shock absorbers were pushed in when your bumper was hit. There will be a visible marking or scraping that shows how far the hydraulic shock absorber was moved.
While you're there, ask him about the damage to the car. Were there surprises when they started the repairs? Sometimes when there is front-end damage, the repair bill does not give a total and accurate description of the trauma suffered by the car. Maybe they took off your bumper and discovered that a part of the frame support was actually bent.
There is a lot more trauma involved in that type of damage than would show in a photograph or by reading the auto body repair bill. Talk to the shop manager, and ask him to discuss with you any evidence of trauma to your vehicle. Ask him to have his workmen tell him when they see evidence of trauma. Have them discuss it with you and offer you the opportunity to photograph it.
At the least, you can get a statement from the auto body repairmen and mechanics that will support your claim that the trauma was sufficient to cause you injuries. Often such trauma exists in the vehicle, even in cases the insurance industry classes as low impact accidents. If that much trauma occurred to your car, think what your more fragile body could have absorbed!