Try modifying your template, calling the nextgen random image function where you want the images to be displayed. Here is the function you need:
nggDisplayRandomImages($number, $width, $height, $exclude, $list)
$number: the number of pics you want to display, there is no default, so you have to provide this. You want to specify 4 images.
$width: the width of each picture, defaults to 75 if you don’t provide anything
$height: the height of each picture, defaults to 50 if you don’t provide anything
$exclude: gallery restriction type:
all means include all galleries
denied means deny the galleries in $list
allow means only allow the galleries in $list
$list: gallery IDs affected by your $exclude
This example uses 4 random images, 130px wide by 85px high, from gallery ID 5:
nggDisplayRandomImages("4","130","85","allow","5")
Reference:
https://www.vuthy.com/blog/2008/11/16/nextgen-gallery-random-photos-from-a-specific-gallery/#instructions.
The above post is old, but it should help.
Good luck!
