I've been looking up pictures of beetles, considering another translation describes Gregor as a bug more similar to that of a beetle, rather than a cockroach. Beetles seem to me, much less disgusting than cockroaches- but maybe I'm biased after growing up in New Orleans. Anyway, seeing pictures of the beetles makes me feel even more sympathy for Gregor. They don't look very imposing or grotesque. Their gray/black color makes them seem sort of melancholy, almost pathetic.
Here's a picture of a beetle I thought seemed particularly Gregor Samsa-esque. Lonely, alienated, shameful.