This is a fun one. Salvador Dali’s stuff is so chaotic that I always have trouble sorting out everything that’s going on.
The (probably ringing) telephone suspended above the central figure looks to be a clever metaphor for artistic inspiration; a device which commands attention and delivers communications from who-knows-where.
The crutch holding up the painting arm is an interesting bit of self-deprecating humor. It rests on the orderly frame that is meant to contain the natural growth of the tree, which is almost aggressively overflowing its boundaries (and is vaguely shaped like a human figure).
The mausoleum with the cypress trees and the brooding brick figure with the clock face together represent time and mortality, looming behind the artist as he struggles so frantically. The hole over the brick figure’s heart matching the door of the mausoleum describes the feeling of despair that these things bring.
There’s a lot more in the picture of course, I’ll have to give this one some further study. Funny to think of it being made for an advertisement. Thanks for posting.
I'd be very interested to hear your interpretation of the car in the background next to the bricked figure, which is branching out of a tree connected to what seems to be a pillar, a fault or a pile of giant books.