The interior fillet will do a lot to disguise and hide any light leaking throughthose holes, but you can do a decorative finish by filling the holes with round toothpicks after you pull out the wires.

If the holes are too big for toothpicks, find yourself a pencil sharpener and a few pieces of scrap wood. I think the school type of desk-mounted, or wall-mounted pencil sharpener is the tool of choice here. some of these accept pencils of various diameters and will take dowels or round edged stock of varied dimensions.

As for the type of wood, cedar is preferable, but pine will work. You'll only need a little. Commercial dowel rods will work too. Get one that is about 3/16" diameter or slightly bigger. If you have any friends who are into archery, see if they have any broken arrows. These tend to be from Port Orford cedar, and 5/16ths in diameter. Running the end through a pencil sharpener removes the paint from them, too.

Cedar strips that are trimmed down to 1/4" x 1/4" can have their edges roughly rounded with a utility knife. they then go into the pencil sharpener and are "turned" to fine, tapered "pencil points" (without any lead in them). A drop of glue in the hole, tap in this pointed stick, and use a chisel or utility knife to cut it off a bit above the surrounding wood. When the glue dries you sand it flush and it looks like a perfect round peg. Very decorative.

Hope this helps.

PGJ