A sniper ghillie suit is a ghillie suit which does not have the natural jute or synthetic material on the front portion of the suit. This is because snipers spend alot of time prone and crawling on the ground. Any material on the front portions of the ghillie suit would just hinder his movement and also get snagged on all sorts of twigs, brush and dirt.
Most sniper suits also include padding on the knee, thigh and chest area. This padding may consist of a rugged and durable cordura layer sewn over soft pads. This will give the sniper some comfort as he lays on the ground. Some may also include padding on the elbows and forearms.
Sniper ghillie suits can also be heavily modified to include items such as a Camelbak water supply mounted in the upper back to pockets that are easier accessible while prone.
Below are photos of Ghillie Suit Clothing's sniper ghillie suit that is built on military BDUs. Click on the link to see more sniper ghillie suits.