Out of that batch, the first is the best. The focus stands out, it blends nicely with the background, and while the background has a lot going on, it fits well enough. The others need work, especially when it comes to blending. Generally, you don't want your focus to be transparent. You want it to stand out. The background is meant to compliment it. When it comes to backgrounds, there doesn't need to be a whole lot of stuff going on. Some of those look like there was too much going on and it's messy. Since it looks like you're using c4ds, use ones that compliment the render/focus - try to have some sort of flow.