The painting in SungMo’s room is the “Allegory of Prudence” by Titan. It’s hanging in the National Gallery of London.

The three male heads represent three ages of man: old age, adulthood and youth. In the upper part of the painting there’s an inscription which explains the painting. “EX PRAETERITO PRAESENS PRUDENTER AGIT, NI FUTURUM ACTIONE DETURPET” or “From the (experience of the) past, the present acts prudently, lest it spoil future action”.

Here’s the best explanation that I found about the symbolism of the beasts.

…the motto further comments on the corresponding three animal heads – wolf, lion, and dog. This tricephalous creature, in association with an encircling serpent, originated as an attribute of the Egyptian god Serapis and became an accepted symbol of time:

the lion’s head, according to the fifth-century writer Macrobius, “denotes the present, the condition of which, between the past and the future, is strong and fervent by virtue of present action;

the past is designated by the wolf’s head because the memory of things that belong to the past is devoured and carried away;

and the image of the dog, trying to please, signifies the outcome of the future, of which hope, though uncertain, always gives us a pleasing picture.”

source: https://www.titian.org/an-allegory-of-prudence.jsp

If I were to interpret the significance of this painting to our story and, connect it specifically to SungMo, I’d say that it serves as a cautionary reminder for Sungmo to exercise prudence and behave with circumspection. He has to think of his younger brother Lee Ahn who looks up to him and idolizes him.

We see how SungMo likes to say, “I didn’t think this through” (remember Ep 4 at the housewarming dinner?) and he doesn’t want to rush Lee Ahn’s psychometric powers. He’s been acting prudently just as the painting exhorts him to.

Moreover, although SungMo’s memories of his horrendous experience will haunt him forever (alluded to by the old man in the painting), he tries to ensure that neither Ahn nor Jaein (represented by the youth in the painting) will suffer from his past.

It’s funny that Lee Ahn owns the dog because he’s the youth in the painting.

I’ll wait for both episodes to be fully subbed before really watching them; I skimmed through Episode 5 last night but I only ended up muddling through it.