Is there a card that can give all creatures island walk?
{Stormtide Leviathan} is as good as it gets.
Yeah but if you're making an island walk deck that's auto win.
There isn't a card that gives all your creatures a walk (that I know of). Think about it, it'd basically read "if your opponent is playing *insert colour*, that player loses the game." There's a reason they don't print cards like that anymore. It's a stupid way to die.
You can use {Traveler's Cloak} for an individual creature.
This probably doesn't belong in rules, btw.