Matt
I sell all kinds of photos but my best sellers are upscale homes and new cars, which I usually isolate on a white background. I do sell some nature type shots but just not all that many. My best selling nature shot was taken last October and has sold 319 times so far just at one site. Weird thing is it doesn't sell very well at any of the other 9 sites. Thats not that unusual though. Each site has its own best sellers. I don't do any model type shots although those are very popular. Those also require a model release.
Heres a link to the site where its selling well.
Heres a link to my gallery at one of the sites I sell photos on.
Dreamstime Gallery