I have multiple .png files (for example: pic_001.png, pic_002.png... pic_200.png). These are basically separate pages of the book.

I want to create a single printing job, that will print 2 such pictures per one physical page - so it would look like a usual book spread.

I've tried to do this like this:

 lp pic_001.png pic_002.png pic_003.png pic_004.png -d color-printer-1 -o sides=one-sided -o number-up=2

but it was printing only 1 picture per 1 page.

The same result with the for-loop: 

 for i in `seq 1 2 8`; do lp pic_00$i pic_00$[$i + 1] -d color-printer-1 -o sides=one-sided -o number-up=2; done

but also this creates separate jobs per pair of pictures.