The source to generate the image is available.
You might wonder why a wizard would construct a boulder trap with steel spikes mounted on leather bands. The answer is: he didn't. The illusionary boulder in the gaming session was just a regular rock. This image was adapted from a much earlier rendering created back in 1999 for the Return to the Tomb of Horrors campaign. The original boulder was made to look like a boulder trap from Dungeon Keeper, an incredibly cool game from 1999 which a number of the players enjoyed back in the day.
The source to generate the image is available.