Have some kinda cool HTML5 transition when you hit the next button. The site itself is just a cool site, so people expect nice looking animations. Instead of generating a random integer and passing it in as an 'id' in your php script, you should look into keeping everything static except the main box itself. To do this, you need to use JavaScript (preferably jQuery, also look into CoffeeScript) Keep the logo at the top and the 2 tiles at the bottom for social media the same. Don't make the site reload everytime you hit 'next'.

Design-wise, it's great. Very clean and simple, and the logo's cool.