Normally, the effects of the Slow Time dimension on paintings only changes it so the subject is looking at their watch. For the painting of Grandma Triwrangle, however, all that changes is the sudden addition of the Grim Reaper in the background and an Oh, Crap! expression on her face.
Quadwrangle points out that thanks to the IDS glove, the player character won't be affected by the dimension's theme. A loading screen tip points out how this is a good thing, "you wouldn't want lungs made from cotton balls."