Awesome free discrete camping along the dirt BLM roads right after you pass the petroglyph site. Lots of RVers seem to like the area but I always camped in my van. Word of warning after it rains though, it's easy to get stuck in the mud.
The Parowan Gap is a gorgeous place that contains numerous petroglyphs, rock climbs, hikes, and geocache to keep you busy. We stayed in the nearby 3 Peaks Rec area which has lots of amenities including a very large group site, picnic tables, and an 18 hole disc golf course! Definitely a spring or fall site as there is not much shade and it gets hot even in May.