This looks like what happened to my old Samsung TV after about 10 years. There are these little clear plastic things that are glued to the LED's in the back of the TV that diffuse the light used to display the picture through the LCD front panel. The glue used to attach them eventually fails and the little plastic diffuser fall off and that causes the shadows. I attempted to repair my TV which after 10 years was well out of warranty, I was able to disassemble, re-glue attach the lenses and reassemble the TV, but more fell of the next week. It takes me about 3 hours to disassemble and reassemble the unit... There are many fiddly and delicate parts and there can be lethal voltages inside I do not recommend doing this unless like me you are an experienced electronics repair person..... in the end I decided to just buy a new TV and send the old one to e-waste recycle with a note that it was probably good for parts.
