Minecraft will duplicate/spam different parts of the world when offline. It chooses a chunk and will display that everywhere while switching what chunk it displays. Please Note: this ONLY happens when i'm offline using no internet connection!
PS: I am using a texture pack at the moment, but it does the same thing with the texture pack off, so it's not the pack. I have tried reloading the game/world and it wont fix it until I connect with the internet again.