To be honest with you I would like to think that Mail Chimp will have spf records and domain keys etc all sorted out and generally keeping the reputation of their infrastructure clean.
Hence I would imagine this will be issues with your content and interactions from your recipients.
A couple of things I have noticed straight off.
It looks quite image heavy there are spam rules regarding the balance of images to text.
My understanding is that spam filters cant check what is on an image hence is one preferred route for spammers to use. You can apparently fill the images alt text with a couple of relevant paragraphs to circumvent this. But make sure you dot just use the same paragraphs lots as this will look like duplicate content.
In addition to this there are a bunch of online tools that can check for spammy characteristics of your message. Such as -
http://www.emailspamtest.com/
http://isnotspam.com/
Also an issue we had was people who no longer wanted our emails just junked us. This is really damaging for your reputation its much more preferable that they subscriberunsubscribe. We moved our opt-out link to the top of our email and made it prominent rather than in the footer text and we belie that this helped.
Also the frequency and relevancy of your email messages to your users will also affect the number of times you are junked.
Deliverability will always remain somewhat of a dark art though - good luck!