Website viewers need a place to focus on when they first arrive at the site. Generally, that place will be an image, and it needs to be an image that communicates the message of the site. When there are too many images, especially if they are of equal size, the images cause confusion, instead of being helpful.
In the process of trying out a new theme for MontanaWebmaster.com, I found myself with an image explosion. The combination of the banner slider and the 4 images below it are just too noisy to pick out a focal point.
So, I will try for photos in the second row to be more towards gray scale. Experimentation will let me know how close to black and white I have to get.