We spend a week camping down stream from Mirror Lake. This is a busy area for ATVs and camping spots are some times hard to get. There is USFS campground at Mirror not very big-- nine sites I believe. Didn't see any sites that I thought were big enough for our TT (28 ft).
There is dry camping along the road from Taylor Park Trading Post to Tincup. Also the three mile road from Tincup to Mirror Lake has dry camping along it. Again these may be full. The road from Tincup up is rough but doable. Tincup pass was still snowed in two weeks ago so didn't get over to St Elmo. Lots of ATV trails in the area.
Mirror Lake is a small lake with fairly good fishing it is at the base of Tincup Pass. If you are a four wheeler Taylor Park has a lot to offer. You should be find a spot to camp somewhere up there.
Check out the Gunnison NF web site there NF campgrounds north of the Trading post where you can ride atvs out of. Lake View campground is just south of the trading post but no atvs are allowed.
We have been up there three times now and it is be coming one of our favorite areas.