It should be noted that for all of the "packs", you only need to do the big download once. After that, whenever the pack updates, you only need to download all the changes between the current version and the last one you downloaded. They also work for new games, as well as the new updates working for old games, so it's a one time download investment, so to speak.
The MegaFacepack 6.0 Size: 6GBThe MegaFacepack is a graphics pack containing over 100,000 faces of the real life players in a huge variety of leagues, which is essential to both make their player pages look decent, as well as to actually remember who the hell they are. Download available in both standard browser based, and torrent.
Metallic Logos Pack 2014 Size: 3.3GBSimilar to the MegaFacepack, the
Metallic Logos Pack includes logos for nearly every team in the game, including ones that will likely never reach the playable leagues in a standard length playthrough. More importantly however, is the fact that it includes logos for teams and competitions in the top tiers that SI does not have the rights for (They are able to have the real names of teams and players for almost every nation, but not trademarked logos) , meaning without them, the game has to use a generic colortone crest.
FM14 Real Names and German National Team Fix Size: Negligible, not even half a MBAKA
The "Stop Generic League Names" pack. This gives many leagues in the game their real name, as FM can't have them for sponsorship reasons. For example, England's top league goes from being called simply "Premier League" to it's proper sponsored name of "Barclay's Premier League". This applies to many other national leagues that FM couldn't get a license for from the sponsor holders. In addition, it makes the German National team not use "ghost" players instead of a real team. Again, Germany's national team for whatever reason has a copyright holdout or similar, so FM had to make their national team only use generated players that don't really exist in the league. This file also fixes that.