Fireboard

I then glanced round the room; and besides the bedstead and centre table, could see no other furniture belonging to the place, but a rude shelf, the four walls, and a papered fireboard representing a man striking a whale.

Source: wiktionary

1915, Mary E. Wilkins Freeman, Emancipation A stovepipe had been fitted into an iron fireboard covering the great fireplace

Source: wiktionary

The wind whopped and spat into the chimney; and now and then a puff of wood-smoke blew out and mounted up along the blackened fireboard.

Source: wiktionary