WIP, I’m not sure LB is talking about the front covering during the chuppah (known as a deck-tuch) or the veil that goes down her back.
Chareidim cover the face of the kallah during the chuppah with something that cannot be seen through. It is usually a beautiful piece of lace with a backing so that no one can see her face during the chuppah. It is only necessary to be as big as her face and to cover as far back as is necessary to pin it to her hair to keep it from falling off.
The veil going down the back can be as long as one likes, for all walks of life. I have seen some that have a very long train, but usually something to the bottom of the lower back area is usual. My daughter had an extra one that was very long just to add to the pictures. She did not wear it during the rest of the chassanah. The back veil is usually made of more than one layer and non-chareidim will take one of those layers and cover the face of the kallah with that.