By playing through the various modes of the game, you can unlock a wealth of extras:

Adidas Etrusco Ball
Win an 8 (or more) Team Custom Knockout Tournament

Adidas Tricoloure Ball
Win a 5 (or more) Team Custom League

Classic 11 Team
Qualify for the World Cup in Road To The World Cup Mode

England 1966 World Cup Kit
Win the International Masters Tournament with England in Road To The World Cup Mode

England 1990 World Cup Kit
Win the International Open Tournament with England in Road To The World Cup Mode