Hmm, this should have changed to a World Cup graphic by now...

If you do not want to see changing "snippets" on the home page, you can suppress them. These threads list a variety of different methods for that:

• How do I turn off the animation when I'm on the Firefox home page?
• How do I stop my homepage from showing the bouncing star that tells me to get started using bookmarks?

If this isn't on the built-in Firefox home page, it could be caused by an add-on. To rule out one of your extensions is involved, could you try Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

Not all add-ons are disabled: Flash and other plugins still run

After Firefox shuts down, a small dialog should appear. Click "Start in Safe Mode" (not Reset).

Any difference?

Why don't you just use a different "homepage"? There's no "law" that says you have to use the default homepage. See - How to set the homepage

For those who are don't like the about:home graphics {web link}