I have a lovely book on ponds that my wife gave me, my first thought is that natural looking was perfect, but there are so many "formal" ponds that made me think that would look equally awesome. When it comes down to it you need to figure out a style you're looking for. Would your long skinny pond be up against a house? Or used as a border for something? completely in ground or partially above?
I had a small pond a while back, where I basically had plants in it (whatever ones Home Depot would seasonally sell) one day all of them were ripped to shreds, I suspect raccoons that were looking for fish that did not exist, and that was the last of my pond days.