It's really easy.
Just change your "Image" post type template in "Settings" -> "Templates" -> "Images" to:
Code:
{#preview#}
-
Name: {#folderName#}
Total images: {#totalTypeFiles#}
Size: {#folderSize#}
Formats: {#typeExtensions#}
-
{#links#}
You can find preview settings in "Settings" -> "Process" -> "Preview".
Change rows and columns to what you need.
By default images are combined into single image for preview, but you can disable that option and then you will have single preview images (rows * columns = total images for preview, for example if you need total 6 images just set rows to 2 and columns to 3).