I have just found out that the world generation methods in the 1.7 alpha version of Spigot are identical to the 1.6.4 version. Worlds generated in 1.7.2 vanilla servers look completely different. That means that the work done yesterday to find a valid seed and to try to show you an early map was for nothing. We will have to wait for a better version of spigot/Bukkit after all. Sorry for the unjustified hype!
Turns out the spigot version was a 1.6.4 version made to accept 1.7.2 clients, not a 1.7 version itself.