Black cars are commonly known to represent death and funerals. This is known because people wear and drive in black cars to mourn the dead. "About five o’clock our procession of three cars reached the cemetery and stopped in a thick drizzle beside the gate—first a motor hearse, horribly black and wet."
The eyes of T.J. Eckleburg represent God watching over. Wilson states it in the book and it also reoccurs often before and after a bad event. "‘I spoke to her,’ he muttered, after a long silence. ‘I told her she might fool me but she couldn’t fool God. I took her to the window—’ With an effort he got up and walked to the rear window and leaned with his face pressed against it, ‘—and I said ‘God knows what you’ve been doing, everything you’ve been doing. You may fool me but you can’t fool God!’ ‘