This is the great 'The Crusades' mod by Caius Britannicus, featuring two factions (Crusaders and Saracens), 52 tpy, hundreds of units, new campaign map and much more. The mod isn't modfoldered, so it requires a fresh installation of BI 1.6. Just launch the installer and be sure to target your 'Rome - Total War' folder.
Nice mod but fixing difficult
Thanks Nelduin for this upload. The Crusades mod is really worth playing.