It's not recommended to use google images on your website since the images on google images are not actually owned by google.
Images shown on Google Images come from other websites so the images would belong to the website owner.
So you'd need the images owners permission to use the image.
However I find that some people use Google Images on their blog but then link back to where the image was found but always download the image to your computer and host it on your own server so you don't use the other persons bandwidth on your website when the image is downloaded.