With ImageMagick you can create a photo collage from the command line in Linux. I’ll show you how!
First, make sure you have ImageMagick installed:
$ sudo apt-get install imagemagick
Next, to simply slap photos together into a grid style collage, use:
$ montage *.jpg collage.jpg
There are tons of options for montage. See this page for an incredible amount of detail.
I like to take family photos and use this command to make a collage:
$ montage *.jpg -border 2x2 -background black +polaroid -resize 75% -geometry -60-60 -tile x6 final.jpg
The end result looks like this:
(blurred out here for privacy)