Edit - appears that the theme is half price and not free as advertised. I've updated the link in the OP to the free theme for Outbreak Day 2019.
There is some discussion on HUKD that suggests you can get the Ellie theme for free if you hit the back button.
The Last of Us Part II Ellie Theme
Note - this theme will be available from 1am 27/6 AEST.
Please note: This content will be free from 16:00 (4pm) on 26 September until 16:00 (4pm) on 27 September. After this point, this content will cost £2.49 (A$4.55).
What's a PS4 "theme"?
Isn't this just advertising for the game?
(note: I wish I could have played the original game but didn't only having a PC)