Put these Python scripts in your "plug-ins" folder (e.g. "C:\Users\Faxmachinen\.gimp-2.8\plug-ins"). You may have to right-click the link and choose "Save link as...".
This script turns all layers into a sprite sheet.
Filter > Animation > Sprite Sheet...
This script adds a border to make the result look like a Polaroid photo.
Image > Create Polaroid...
For best result, crop the image to 1:1 first so the script won't do it for you.
This script takes two color layers and two corresponding depth map layers and merges them three-dimensionally.
It works with 8-bit (grayscale) and 24-bit depth maps.
Note that a depth merge filter is already included with GIMP, but it does not support 24-bit depth maps.
Filters > Combine > Depth Merge 2...