Some ideas:
If you can be there during operating hours, stop at the BLM office in Caliente (on the left as you come into town) and ask for a map of the Silver State Trail, or download it
here. The trail runs west of Pioche, but you can do different sections of it from various points. You'll probably see one for Chief Mountain OHV, that's strictly an ATV only trail system. Though some of the trails overlap Jeep 2 track trails at times, the main routes are blocked access so anything bigger than an ATV can't get through.
The BLM map is pretty decent, not as thorough as one of the before mentioned Atlas's, but it has some good sites to see listed. Bristol Wells west of Pioche has some old buildings to see and charcoal kilns as well. You can take the Pan American Mine road west of Pioche (off SR320) around the backside of Highland Peak and come back over Stampede Gap to SR320. There's also a place called Big Pines off the Highland Peak service road that has some really old silver spruce trees that are well over a 100' tall, makes a nice picnic area. Also the "back" road from Eagle Valley to Echo Canyon/Rose Valley is a nice trip, even though it's asphalt. If you get lucky, you'll see some golden eagles flying around in Rose Valley. There plenty of sites to see that aren't off of a dirt road though. Most all of Pioche is a photo op. Kershaw-Ryan State Park (outside Caliente) is a very nice stop as well. I haven't been there recently (the park), but the drive to Beaver Dam State Park is nice, and Barclay is worth a picture or two. Even Cathedral Gorge is worth the trip if you haven't been there.
You can also download a rock art guide here:
Lincoln County mapsTo be honest, I know of a nearly endless supply of stuff to see up there, it's just hard to tell someone how to get there on a message board and there aren't too many maps that show you how to get there. Even with GPS coordinates people can get lost, and the NV/UT state line in that area isn't the best place to be lost. If you can make it, the run I'm leading for Lincoln County in June (posted in other runs section) would give you a good idea of what's up there.
BTW, if you haven't been to the Horsethief camp grounds yet, they are primitive, meaning very little other than a fire pit, some trees and a pit toilet. But they're free.