Good start JoÃƒÂ£o!
I should preface by saying I don't know much about Maori themes and styles, so strictly speaking, I will be coming from a design standpoint and looking at how to strengthen your choices here. I may be a bit long winded, so I apologize in advance :P.
The first is try to think of the layout using a grid. This doesn't have to be visible to the users as lines, but giving a cohesion to all the elements will really help. A great visualization of this can be seen here:
That is a blog post by a designer describing his use of grid. He uses a red overlay to show where the grid exists, but in actuality it is used as a guide during his design and coding process. He doesn't use the red columns anywhere on the site for look, just on that particular page to show his example. There is also an excellent PDF on that page describing grid and it's uses much more in depth.
To apply this to your mockup, I would suggest using your top nav as perhaps the starting point for this grid. You have a series of elements that can serve as a foundation for column widths. You can use a series of columns to horizontally line up where elements will fall on your page. This will give it a much stronger visual cohesion as people read the page top to bottom.
Something a bit more specific, I like the use of serif'd fonts in your top nav, I would suggest playing with serif'd fonts in your document as well. It will lend to that natural feel you are trying to push with this design. San-Serif fonts often represent technology and machinery, and therefore may not be the best choice in this design.
I reflect some of the earier posts regarding the header. A cleaner integration on the font will help tremendously, perhaps making it bigger, losing the drop shadow and finding a way to get it to creatively interact with your green banner.
Some questions I have are, why the use of paper? What does it represent?
If these are all very implortant themes, then try to integrate it better. It looks like you spent a bit more time on the top nav, header and background than you did on the content portion. Try to think creatively on how to deal with your content and secondary nav. These could really play or work into each other so they can somehow connect visually.
Some techniques I use when I design, I constantly ask myself why I am doing what I am doing because I often find myself falling back on old tricks and techniques that don't necesarily work with my new work. I do not mean to imply that you are doing this, but it will serve you to always justify everything in your design, and not just 'because it looks good'. You could grab a hundred awesome looking pieces of different websites and throw them onto the same page, that won't make a good website.
Anyways, I hope this gives you some ideas and answers some questions you have been having! Kudos for having the guts to post your work publically and have it be critiqued by the general public!
Keep up the good work!