Hello there!
As recently stated by someone else, no mobs are on your server because you don't have any in your database
.
See, when you loaded the itemsdump.sql or whatever its name is, that put all those items into the database.
So you need a database, for example, named monsters.sql so you have monsters on your server.
Now, tcsmyworld created an excellent database for 0.5.1.
Search around in the world building forums for his database. Then drop your current database and source his.
Hope this helps