There's a scenic route between Las Vegas and Reno?
Tell me you're joking.
The one time we traveled between Las Vegas and Reno together, I suggested we take the more scenic route when returning during daylight, but you weren't interested.
At least you did see the "stark beauty" of the Nevada desert, north of Walker Lake, that I pointed out, after sunrise, on the way up.
The most scenic route is to take U. S. 395 south out of Reno through the Walker River Canyon (very pretty, especially in the spring time with the snow melt swelling the river as it rushes through the canyon), Bridgeport, Mammoth Lakes, and Bishop (all in CA) to Big Pine, CA. There's a spectacular view as you head south from Minden/Gardenerville, NV, towards Topaz Lake (you don't get this view headed north).
Once you reach Big Pine, CA, take California State Highway 168 east through Lida Pass, near where the oldest living things on earth, the +5000 years old Bristlecone Pines are located, off a gravel road to the north. At the border between CA/NV the highway becomes Nevada State Highway 266. Continue east to Lida Junction and then head south on U.S. 95 through Beatty, NV to Las Vegas, NV.
As ZzyzxRoad mentions there are other ways to go, but I think this route is the most scenic.
I would only recommend this route in the Summer time, warm weather before the snows in the fall, or after the snow melt in the spring unless you enjoy "chaining up". Also, Lida Pass is not plowed in the winter and is, thus, impassible then, so cutting through Death Valley would be the way to go in winter.
If you decide to cut through Death Valley in the winter time, there's a spectacular view of the Sierra mountain range escarpment (especially so, in the winter, with all the snow on top of the mountains) while heading south on U. S. 395 between Big Pine, CA and Lone Pine, CA. (When cutting through Death Valley take the Lone Pine, CA to Beatty, NV route). Again, not easy to see the spectacular view while headed north on U. S. 395.