>>/2211/
Duh.  The output needs to be PNG, not JPG.  Let's try that again.

combine.esh (emacs eshell script)

setq g gap.1000.transparent.png
convert -append 2010493173248692712_1.jpg $g 2010493173248692712_3.jpg $g 2010493173248692712_4.jpg $g 2010493173248692712_2.jpg out.transparent.png