To install the MTG Game Definition, add the OCTGN Game Directory to your list of Game Feeds. Paste this URL into the ‘Add Feed’ window inside Games Manager: https://www.myget.org/f/octgngamedirectory
These are the image packages you need in order to view the actual card images in-game.
All sets prior to Return to Ravnica Block - This is a magnet link to a Torrent, which should automatically load your default Torrent client when you click it. Currently, torrenting is the only method to obtain these older images due to its large size (~4 GB). THE IMAGES ARE ORGANIZED BY BLOCKS!
Additional image packs not in the torrent (direct downloads):
Tokens v2 (updated September 6, 2013)
Commander 2013 (Hi-Res) v1 (April 16 2014)
Born of the Gods (Hi-Res) v1 (April 16 2014)
Special thanks goes out to the folks at http://www.slightlymagic.net for their amazing high-resolution card scans!