Here's what the "offensive" wallpapers look like:
This person called for a boycott of Facebook over these "Zionist" symbols (autotranslation to English)
This one issued a warning to his readers about accidentally promoting the "symbol of Knesset" and Star of David:
The Palestine Today article notes that it is not easy to see the details of the wallpaper and its horrible Jewish symbols until after one posts on Facebook, which causes great embarrassment to the antisemitic posters.
It takes roughly three seconds to edit a post and change the background, but if someone gets a screenshot in the meanwhile, the shame of promoting a Jewish holiday might be too much for some people to stand!