Draping length

You generally want it to flow all the way to the ground. An abrupt end can look odd and have a little bit of drape piled onto the ground helps it not move so much. Some stylization tricks of the drape is too short is to start from one corner to the other side like the first photo or hide the end with flowers (or lace, ribbons, ect. to match whatever theme you may have or want) like the second.