The redundancy in the commands could easily be shortened to something like ./terragen -p /home/was/Terragen/Projects/Background_Galaxy.tgd -exit -r -f 42 -o /home/was/Terragen/out/ -fn Background_Animation.IMAGETYPE.%04d.tif
For the main render, it would simply omit ".IMAGETYPE" from the filename.
Considering extra outputs, in a commercial setting (and even me trying to play with them) should be common-place the node could be smarter, and the docs more condensed.
It could go further and not even need the IMAGETYPE unless someone wants a custom defined naming convention, and add the image type before MIME type.