Black-and-white images of nature form photo cubes, which can also be used as bookends. The photographs aren't glued to the cube. Instead, a special gel is used to transfer the images onto blocks. Transfers last longer than paper photographs, so this decoration can remain a fixture for years.
Plain wooden cubes are available at crafts stores, as is the soft-gel transfer medium needed for this project. Bear in mind that the blocks require a fair amount of drying time as each transferred photograph sets.