How to keep website homescreen image size proportionate to aspect ratio

[lukeoneill90]

Hi, 

I have created my site, which is nearly finished and looks great on my mac. However, when swapping to a desktop with a much larger screen and wider aspect ratio, everything looks awfully positioned. 

My main concern is keeping the image sizes proportionate to the original design intention I had. 

Mac (Design intent) 

Desktop (Wider aspect)

I have other pages also which should fill the page, until the user scrolls to see more. 

Various Pages like this. 

Please help!

Kind Regards,

Luke