I have a large single bowl sink and a smaller, matching prep (bar) sink. Is it going to look strange to put them back to back in my island? It's 4' x 6' and there's nothing else on the island. Thanks.
I haven't ever installed two sinks in that small of an island.
but the real question should be how much use would the prep sink (salad sink) get? if you regularly have help in the kitchen to where it would get that kind of use, I would probally think about shifting them so they at least aren't back to back. Kitchens have to be functional, and if two sinks on your island are going to be used put special attention on faucets and making them ornamental so they add to the kitchen decor and that will help it not look odd. maybe even look at designer sinks
Two sinks might look unusual on the same island, especially if they are back to back. I would suggest moving the entertainment sink off the isalnd to a different location, or getting rid of it altogether. Some people regret installing the extra sink simply because they do not use it. Again, it depends on how many cooks you have in your household.