OK, well maybe ISO does not have nearly the impact on your creativity as the other exposure settings, Aperture and Shutter Speed. But it does have an impact, however limited, so it should be discussed.
ISO
As we have discussed, ISO controls how sensitive our media (film or digital sensor) is to light. At higher ISO settings the media is more sensitive to light, meaning that you need less light to create a properly exposed image. So at ISO 1600 you need a lot less light to take a photograph. However, the higher the ISO the more grain, or noise, you will see in your image. Today’s digital cameras are doing an amazing job of taking photographs at high ISO with a minimal amount of noise. Combined with the available photo processing applications of today, it is becoming easier and easier to get good results when shooting at a high ISO setting. However, some times you might just like that grainy effect and want to keep it.
Summary
Like with our other exposure controls, the choice is up to you. These settings are simply tools that help you to create the photographic images that you desire.