You can use your own image for your meeting background when you also use the NONE theme.
To change the background of your meeting:
1. Select Settings, the gears icon at the top.
2. Within Meeting Settings, select the Custom Theme tab.
3. Select the 'Browse' button and navigate to find the image you wish to upload.
4. Select Control Room from the tools icon.
5. Select the Themes tab.
6. Select the NONE theme.
Your new background image is now active.