This one? The Royal Mint refers to beads, rather than pearls.
As for a reverse design, expect the Daily Mail to start a campaign for the restoration of that Greco-Roman whore, Britannia. Its hordes of reactionary readers would probably respond enthusiastically.
My first thought for a design was Stonehenge, but given that it's a small bimetallic coin (22mm in diameter, I believe), the reverse design would be rather small, unless it was allowed to spread over pill and ring. But I'd say Stonehenge still wouldn't fit, so I have no decent suggestions.
The current status of pound coin designs is that Dent's full jigsaw design appears yearly (correct me if I'm wrong), while designs for each nation also circulate concurrently - e.g. the daffodil and leek for Wales, etc.