Here's something to think about from Elizabeth Edwards and Janice Hart in the introduction of their book, Photographs Objects Histories: On the materiality of images.
"...a photograph is a three-dimensional thing, not only a two-dimensional image. As such, photographs exist materially in the world, as chemical deposits on paper, as images mounted on a multitude of different sized, shaped, coloured and decorated cards, as subject to additions of their surface or as drawing their meanings from presentational forms such as frames and albums. Photographs are both images and physical objects that exist in time and space and thus in social and cultural experience. they have volume, opacity, tactility and a physical presence in the world and are thus enmeshed with subjective, embodied and sensuous interactions. These characteristics cannot be reduced to an abstract status as a commodity, nor to a set of meanings or ideologies that take the image as their pretext. Instead, they occupy spaces, move into different spaces, following lines of passage and usage that project them through the world. As [the chapters of this book will demonstrate in various ways], thinking materially about photography encompasses processes of intention, making, distributing, consuming, using, discarding and recycling, all of which impact on the way in which photographs as images are understood."