Last week I went to Swallowhead Springs. It was garlanded in late summer flowers, perfect. Except there was lots of crap there, marring the perfection.
Yes, this is the problem isn't it. No-one seems to mind too much flowers, leaves, a pebble or a few small ribbons but when it escalates into plastic dolls, crystals and graffiti it does become intrusive. Perhaps by leaving only small, natural objects that will degrade fairly quickly in the open would be one answer. 