It can be hard to put a lot of time into something and then be told it's no good. Trust me, I know how that feels, and if you look around these forums you'll find that you're not alone in this. I'm sorry.
Here's my advice for you:
Take a look at some of these guides, and try to learn the tileset and create levels based on these guides. Practice by example.
http://forums.graalonline.com/forums...ad.php?t=47045
Good luck!