XF 1.5 [SOLVED] SSL issues

Hi all!

Firstly, apologies if this is in the wrong category.

So I've recently bought a WildCard SSL Certificate from AlphaSSL, and I'm trying to set this up on my forums (xenForo 1.5.2).
I've updated my Basic Board Options > Board URL to use https (I set it to 'https://opfactions.net/').
When I try to load the pages, the CSS goes, well, gone. The CSS fails to load, as it decides to load via http.

I am running nginx, rather than Apache. This is my nginx server block: http://paste.md-5.net/yipifuqufo.nginx

Any help would be appreciated. :)