Sharing a picture of our Fireplace Mantel, that my husband built. I sadly don't have a before picture- it was textured dry wall on the sides-and tile surrounding the fireplace -where the brick is now with no mantel on top to set decorations on.
My husband built the top mantel portion first, with (2) 1 inch thick piece's of wood-thick enough to allow for pictures-items to be set, then added crown molding underneath it, then some smaller molding to add more detail between the two-
A long thin flat piece of plywood he cut and used as the front portion-adding a tiny piece of molding trim around the edges.
On either side we found some long pieces of plastic like stuff-with deep groves-and attached it to both sides-then adding a thin piece of molding on either side of that to finish it off-
So basically just layering molding on top of each other-
The portion that was tile- we just sanded lightly and used thin bricks and cement and spread the cement over tile-used tile dividers for spacing between each brick-to then spread more cement all over the bricks- and then wipe down which gave the bricks a more toned down color.
Here are two more closer up pictures of brick-and molding-
Just an idea of how you can add some character to a flat dry walled, Tiled fireplace.