In nature photography, one of the best things to find is some subject with contrasting colors. Of course, you are taking about nature, so it isn’t really up to you, but if you can find a contrasting color (that would be red/green, or yellow/black, or blue/green etc), it will make the image pop out.
Sometimes you have to look REALLY hard to find a contracting color. Red and green are two of my favorite contrasting colors, they just go so well together and each color stands out. In this image, I remember looking around forever for the red/green match and finally found this tiny little spider. Not the largest subject I would have liked, but, a green spider, sitting on a red flower, go figure. Without the green background, the flower itself would not jump out of the image quite as well as it does with the contrasting color in the background.
The spider is about the size of my finger nail at most, so getting in really close was pretty important. Framing the background to have some shade of green was just a matter of framing, and trying to get a somewhat diagonal going from the center of the flower up to the spider is an element of photography I like as well.
Some reviews have not cared for the spider there at all (I do have both shots, but like this one better), and the flower itself could have been a sharper with the focus on the center of the flower (if that was the subject). Since the subject is the spider, he is what is in sharp focus (you may have to click on the larger version to see the detail of the spider better). What do you think? Do you like the spider there or not? He is obviously the subject of the photo, not the flower. The flower is far to soft, but they do tend to compete with each other.