Actually, there is a file that you can download from Photopost, and re-upload in your "Gallery". Then you run it from your Gallery cp. This will create a "product" file that you upload in your vb products section.
This will create a thumbnail strip that you can specify weather you want newest or newest pics. Plus the amount of images you want to show up.
You can make the changes in the Plugin section.
You can see how I have 6 images are 'random' on my
website
This of course, if it's Photopost Gallery