To some, yes. They are pretty neat. However, not everyone cares all too much about football and the world cup, and many don't really like how it was very in your face.
What if Firefox added a widget counting down when a fancy watch brand is going to release their nth anniversary watch? Some people might like that, but most people aren't that invested in watches. Or perhaps a pop up about next-gen laptops and mini PCs, there are some people who would appreciate that, but most people see something like that as an advertisement.
You could put any other topic as an example: innovative display panels, networking equipment, bicycles, fashion, dishwashers, power tools, 3D printers, backpacks, miniatures, whatever. There is a minority of people who would love something like that, but the majority see it as annoying advertisements. A happy middle would be to add these wallpapers and widgets as an opt-in experience, maybe as an extension or something, I dunno.