mosaic maker made for geckocollection.
example
landscape
web version created by @anematode
Recommended specs: at least 4 gb of ram, a decent cpu
Download the zip file and run the exe in the bin directory.
Create an 'input' and an 'output' folder inside the main project directory.
Put input images in the input folder and output will be in the output folder, source should already be ready to use.