Mono photos provide a different look and feel to an image. I have developed to a point now where a significant amount of my processing looks at both mono and colour, often the mono comes out on top. I also have a Fufi XT1 converted to Infra Red which requires images to be processed in mono.
An album showing my current 12 favourite images in this catagory. A full list of all my images can be found on my Flickr Page with links to that below and on the home page. (Two white dots icon)