While some isolations sell well, overall, they are very simple to do, which is why everyone does them.  People, objects, animals, they've all been done already.  You're just cutting into the pie.

If you can create things with carefully planed backgrounds (nice out of focus areas with good mood and sufficiently muted to be good as copyspace) I think you'll have a more defensible niche than isolations.

agreed.  i think there is more opportunity for growth in this area than isolated on white.

I f you have good skills to isolate things than don't waste it by simply omitting isolations. What our friends posted before doesn't exclude isolations.

At my day job I'm a graphic designer, I often need stock photos as illustrations and guess what I use? Yes, isolated images because the paper is white, I don't need copy space and I don't have square frame. I know, many designers use isolated photos like this. Just open some magazines and see the small isolated photo illustrations near the articles.

A important thing: don't isolate completely the subjects! leave a slight shadow so the objects don't "float" in the nowhere, the shadow gives a "surface".

I suggest to you to focus on isolations but on blurry backgrounds too.