Some background on this comic:

Who's got the quote from Discworld about the torturer?

Edit: Here it is:

It has to be said…there was little to laugh at in the cellar of the Quisition. Not if you had a normal sense of humor. There were no jolly little signs saying: You Don’t Have To Be Pitilessly Sadistic To Work Here But It Helps!!!

But there were things to suggest to a thinking man that the Creator of mankind had a very oblique sense of fun indeed, and to breed in his heart a rage to storm the gates of heaven.

The mugs, for example. The inquisitors stopped work twice a day for coffee. Their mugs, which each man had brought from home, were grouped around the kettle on the hearth of the central furnace which incidentally heated the irons and knives.

They had legends on them like A Present From the Holy Grotto of Ossory, or To The World’s Greatest Daddy. Most of them were chipped, and no two of them were the same.

And there were the postcards on the wall. It was traditional that, when an inquisitor went on holiday, he’d send back a crudely colored woodcut of the local view with some suitably jolly and risqué message on the back. And there was the pinned-up tearful letter from Inquisitor First Class Ishmale “Pop” Quoom, thanking all the lads for collecting no fewer than seventy-eight obols for his retirement present and the lovely bunch of flowers for Mrs. Quoom, indicating that he’d always remember his days in No. 3 pit, and was looking forward to coming in and helping out any time they were shorthanded.

And it all meant this: that there are hardly any excesses of the most crazed psychopath that cannot easily be duplicated by a normal, kindly family man who just comes in to work every day and has a job to do.

Vorbis loved knowing that. A man who knew that, knew everything he needed to know about people.

It looks like Larson had trouble figuring out the composition of this comic.

I'm guessing it went like this: He needed to put the sign somewhere that it could be read, so he put it up high. Then he put the door high so that the panel wouldn't have a lot of empty space. But then, he needed to add stairs to the door, and suddenly there wasn't enough room for all of the victims. So, they're hanging in this strange little space next to the stairs that probably wouldn't exist in real architecture.