Let's say I have a web page with a 100 large flickr photos, all IMG tags are referencing the flickr urls. If I get a lot of traffic to this page, will this use my bandwidth consumption because the end user is still viewing these images on my domain or are they loaded from the end user's browser and it will not show up in my bandwidth stats?
They will not affect your bandwidth. This is called hotlinking. Images are stored on another server (owned by flickr) so they will be downloaded from it. When browses will spot your img tags, it will see the reference to the flickr images, so it will download it from there despite the fact the images are on your page.
Note that you do not have much control over hotlinked resources (if they are not yours). And when they are replaced by something else your page will immediately display changed images. You should also have permission to link to someone else's images.