This method will guide you to change your profile picture/avatar with creating a new contact, and then adding a picture/avatar for this new contact in Microsoft Outlook.

Step 1: Shift to the Contact view with click the Contact (or People) in the Navigation Pane.

Step 2: Create a new contact:

1. In Outlook 2007, please click the File > New > Contact;
2. In Outlook 2010 and 2013, please click the New Contact on the Home tab.

Step 3: In the new Contact window, fill your profile references in according fields, and then click the Picture > Add Picture on the Contact tab. See screen shot:

Step 4: In the popping Add Contact Picture dialog box, find out and select your profile picture/avatar, and click the OK button.

Step 5: Complete the new contact creating, and then click the Save & Close button in the Contact window.

Note:
(1). With this method, you can view the added or changed profile picture in People Pane when you reading messages in Outlook 2010 and 2013. However, other exchange users are not possible to view your profile picture/avatar.
(2). You can also add profile picture/avatar to the contact you have already created before with the Step 3 and Step 4 above.

Quickly remove all duplicate contacts from multiple Contact folders in Outlook

With Kutools for Outlook's (Delete) Duplicate Contacts utility, you can compare the specified contact fields to delete all duplicate contacts from multiple selected contact folders easily in Outlook.

This method will guide you to add or change the profile picture for your exchange account via Outlook Web App on internet.

Step 1: Log in the Outlook Web App with your exchange account.

Note: You can quick access the Outlook Web App with clicking the File > Info, ensuring the exchange account is selected under the Account Information, and then clicking the hyperlink besides the Account Settings button.

Step 2: Click your exchange account name at the upper-right corner, and then click the Change below the blank/original profile image/avatar. See screen shot:

Step 3: In the new opening web page, please click the Browse button.

Step 4: Then the File dialog box pops out. Find out and select your profile photo/avatar in this dialog box, and click the Open button.

Step 5: It will take some time to upload your profile image/avatar. After uploading, please click the Save button. See screen shot:

Step 6: Exit your Outlook Web App.

Then you will see your profile photo in the People Pane when viewing emails in Microsoft Outlook 2013 and 2010. What's more, your profile photo/avatar is visible for other exchange users when they receive your emails in Microsoft Outlook 2013 and 2010. See screen shot:

Note: In some cases, you may not be able to view the profile picture uploaded from the Outlook Web App in Microsoft Outlook immediately. Anyway, the profile picture will be visible in several days.