Camping on the Piedra would require hiking away from your vehicle and your raft, but it is more secluded and there are natural hot springs next to the river.
Lime Creek is beautiful, but there will be traffic and most sites are in campgrounds. Junction Creek is a pay per use campground but there are some secluded spots along the creek up the Colorado Trail.
If you don't care about being close to town, check out the Weeminuche, Spud Lake, or Purgatory Flats.
"There is NOTHING--absolute nothing--half so much worth doing as simply messing about in boats. Look here! If you've really nothing else on hand this morning, supposing we drop down the river together, and have a long day of it?" -Wind in the Willows