Just think, you could have one for each major region of Middle Earth - Wilderland, Eriador, Rohan, etc allowing for them to be gradually released alongside the actual RPG supplements.
Within each book it'd be split into sections (sub-regions), in the same way that 'Heart' and 'Rivendell' are, and each piece of art could have a couple of lines of text relating to it; quoting something evocative from TOR or Tolkien's books. The appendices could have a biography plus interview with each of the artists featured as well.
Art in them could also 'tease' future supplements - ie, it would be a collection of artwork already used and that produced for currently unreleased products.
It would also allow for the lovely art from Hobbit Tales to be included as well (and in a larger format if possible).
A great companion to the game, you could use it to easily illustrate places and NPCs, as you flick to the appropriate chapter of the book and show your players relevant pieces; bringing the game to life even more than currently.
Released through Kickstarter, there'd also be a Deluxe option for the book and additional extras to purchase such as art prints of particular pieces and pledge levels for special commissions etc.
I'd love something like this.
