The specific issue being reported in that thread was fixed. If you're still having issues, it's going to have a different cause. I'm more than happy to help you troubleshoot the cause but, given we haven't had any further reports of this, I'm not sure it's a bug.
The sprite sheets are generated and stored in data/local/icons/
, but they appear to 404 on your installation. Do you have any custom mounts or data directories configured? In any case, you may open a ticket with server and XenForo credentials if you like and I will take a closer look.