Hi Pheier,
The above steps are applied in public website. If you just create a blog site internally, we can perform the following steps:
1. Go to the Team Site
2. Click on Site Actions
3. Click on Site Settings
4. Under Look and Feel, click on “Title, description, and icon”
You can upload the picture to site and copy the network location of that picture. Filling in the blank of URL field to see if any improvement.
Thanks,
Johnny Zhang