Images from other servers can not impact bandwidth use locally - they're on other servers!
If you have not done so, enable the UBB Accelerator. It can use PHP's built in compression (if it's enabled) to save bandwidth. Up to 50% of all requests can be fed through the Accelerator, which can cut down the size of each page by up to 75%.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.