I know about the liner and the eyebrows and lipstick tattoo, but is there such thing as a foundation tattoo? Mainly to hide scars, but also for full coverage
There is no foundation that i know of that will effectively cover the scars, because scars are usually raised. Unless there is no raise in the skin and its only a white line or pink line concealer such as DermaBlend may help, which is used for covering birthmarks or even tattoos. (how good it works is still iffy)
Another way to go is scar removal. This is usually not covered by insurance, can be expensive ($300 a session approx.) and can be a few sessions. http://www.scarremovalguide.com/ (that site may give you some info.)
Another option to consider is tattooing over the scars, there are some controversies on this, but usually if you find a tattoo artist with knowledge and experience with covering scars it is possible to make the scar less noticeable. Usually they need to be at least a year old, no keloid scars, because it can make it worse, and black and gray is usually better then color to cover the scars, also a more detailed tattoo thats busy looking hides scars better. http://www.dragonflyink.com/scar_tattoo.html I know people who have done this and they dont regret it whatsoever, as long as you find the right tattoo artist.
Another way is something called dry tattooing, i dont know much about this but instead of using color/ink i think they use distilled water over the scars. It might be hard to find a tattoo artist that does this so you would have to look around.
Hope this helped.