Hmmmm, rock on a roll looks interesting. Wish the pictures were more close up though. I like the skimmer cover idea. I made a faux rock of foam and fiberglass. It ended up costing ALOT and is sharp on the edges.
I'm also looking for inexpensive ideas for edging, but don't want grass or plants. Only things I can come up with are stone (heavy and expensive!) or decking, also expensive, but less heavy. My edge may have to stay just liner for a looong time :'(