Mo,

Let me explain again...
If you want a band of tiles 10 cms high (or 4 inches), make sure that your texture is 10 cms high, and that your box is 10 cms high.

Now give your box the correct length, say 250cms.
It is important that the box is as thin as possible, and that you place it flush against the wall. This way it looks as part of the wall, and will not cast a shadow.

Hans