Tim,
I for one have been enjoying your waterfall shots and I say get as much practice in nailing this shots (learn what settings work and don't work) and then introduce the creativity, it would be a shame to have a great composition and creative setup and find when you download the shot that the exposure or shutter speed was wrong etc
When you are thinking creative, why to con someone to
model for you ? Waterfalls could make a great backdrop, or like in dm55(I hope I got his alias right) shot of M. Pass he had his g/f in the frame to offer interest.
Some other thoughts are, like the bottle of champers pick things that don't below, like a beach ball, or a bunch of bananas, (actually a banana leaf platter full of tropical fruit could be real nice) anyways just let your imagination run wild and see where it takes you.
Can you reverse the centre pole on your tripod to invert the camera ? That could also offer a few different perspectives ?
(Just another though, a wooden boat, or paper sailboat could be another potential prop?)
Hope this helps.