You have the ability to change your office background to suit your mood. To do so, click on your Avatar (your photo) at the top of your office. This will open up your Profile.
Navigate to the 3rd Tab, Office.
Using the first drop down box, click on the drop down to bring up other office choices.
Once you have selected a new office, your background will change automatically.
To add a custom background, create a picture (JPG or PNG) that is 1366X768 Pixels. Save the picture to an online data storage site. You can paste a URL Link from a secure data storage site such as DropBox, Google Drive, OneDrive, etc. into the Custom URL line that will appear when you select Custom in the Drop Down box.
Please note that the URL you use needs to start with an https:// only. You cannot use a URL that starts with http://. Using an unsecured storage space will limit your office functionality. Also, you need to have a url that ends in .jpg or .jpeg or .png.
If you are using Dropbox, you will need to manually change the last digit in the URL address link from a Zero (0) to a One (1)