Majklas on "flexslider to load few images at once"

I was wondering if any (now I'm using flexslider) plugin or gallery script could do this for me: if picture is less than x px, then it would load another fitting picture in the same box.
So to say, I have 900px wide flexslider container, I'd like to show one picture 900 px wide, then other two by 450px. Could they be loaded into one "slide"?
Looking for any options..

Advantages :
no PhotoShop needed to combine those images into one;
use empty space on long narrow images;
get the most info for client;