My 2 cents would be to go as big as you can. I would also shape it so that you are looking across the longest part of it. This is the most pleasing to the eye. Looking across the short part does no justice to it. I would also place the dock in the forefront of the view.
The curvier you can make it look (kidney) the more natural it will look. An island in a 1 1/2 acre pond will consume a lot of dirt and time, I don't think I would do it, you can always place a floating island later.
Make sure to place a lot of structure. Pallets with rock on top of them make great spawning areas in 3-5' of water. Rock areas and a few downed trees also help with cover areas and the "natural" look. Good luck with your project and keep the photos coming!
