beneficial option

Hey there, i'm trying to recreate this design. I was wondering if setting a fixed height and width for the animal images would be the most beneficial option as the size only alters a small amount per device view. I know setting a fixed height and width on containers is mostly a bad practice but as i don't have any child elements that dictate the height and width of the divs containing the images i'm not too sure on the best option whether that be setting a fixed height and width or using a percentage perhaps etc? Any help would be much appreciated.