Good luck with that! That ones a hair puller if I ever saw one. You will never get that to tile correctly because of the angles in the design. Many have tried and failed but uploaded them just the same. You can try one thing.....make your background huge width wise for the top/bottom and height wise for the sides and don't use the TileCenter or TileVCenter. If by sheer luck you succeed the problem you will run into is...how many icons and what size are they that are being used by someone else? You might get close to a somewhat useable background for yourself...but other users won't.

And as a side note: any attributes you have set at zero you should just erase/delete since your not using them...they will only serve to make your file bigger. 

How wide is your screen? Basically what your going to need to do to try and get it to work is....for the top and bottom zoomer make them "almost" as wide as your screen and for the sides "almost" as high. As far as tabbed docks...if you get your zoomers to look ok they will work as tabbed docks provided no one tries to stretch them out...then they will become all distorted...no avoiding it. It's just because of the design of your background.