This is a direct vent gas fireplace where the vent goes straight out the back through the wall. You can frame around this to whatever depth you want that is less than the depth of the front of the fireplace. You can notch out the crown molding on the top of the mantel to accommodate the thickness of the wall you build around it and just leave the mantel in place, or you can remove the mantel and re-frame the fireplace and replace the tile if you want to create a complete new look. From the looks of the depth, you could build a wall unit with cabinets and shelves around it and leave a recess above for the TV.

Not sure what else you are asking.