Here’s a possible fix for that which has worked for me and quite a few folks online: disable Hardware Acceleration in Firefox.
Here’s where to find it:
- Click the Firefox main menu, choose Options.
- Choose Advanced.
- Go to General tab.
- Untick the box beside “Use hardware acceleration when available”.
- Restart the Firefox browser (close all windows including Downloads if it’s open, wait 10 seconds and start Firefox again).
The broken images problem should now be gone – if it’s still there then it’s another problem – please let me know in the comments if you know of any other potential cause and/or solution for that!