When I have needed to include high resolution images in my posts I usually upload and include a link to the image on Flickr. Sometimes the link is to an entire album.
The disadvantage of using an external site is that there is no guarantee that they will still be in place in years to come, and nobody likes dead links in the forum.
So maybe in future, I will attach the normal thumbnail/low resolution image for casual viewing, and, where I feel the need, a .zip file of the original camera's resolution for those who need to zoom in to the minutiae in the image.
Low resolution image:
High Resolution Image