He could get creek rock from a landscaping or pond store. That would look a little more natural. Also try planting some native plants (especially flowering ones) around the pond. This will add more natural looks, as well as attract birds, bees and butterfly's to the pond.
Maybe add some floating plants to the pond? Like water lettuce, etc.
Maybe try adding a bench/sitting area as well, so that you can sit and enjoy it, rather than having to stand.
Lastly, he could add a waterfall to one end of the pond. That will improve the looks, filtration, and aeration of the pond, all good things.