I've defined contact photos for two different contacts using Thunderbird Address Book. SOGo Connector Thunderbird extension is used to synchronize personal address book. First contact has "uploaded" photo, ("On this Computer" option on Photo menu), while second one is using referring URI ("On the Web" option on Photo menu).

Contacts data is correctly stored in the database:

c_content field for first contact contains:
PHOTO;ENCODING=b;TYPE=JPEG:$BASE64_ENCODED_DATA

c_content field for second contact contains:
PHOTO;VALUE=uri:$PHOTO_URI

Thunderbird Address Book is displaying photos for both contacts properly.

However, contact photo is not displayed in SOGo Web Address Book if photo is containing referring URI.

Photo is referring in the following element on web page:
<span class="photoFrame"><img src="https://fqdn/SOGo/so/USERNAME/Contacts/personal/CONTACT-UID.vcf/photo&quot; class="contactPhoto"></span>

Web browser is sending following request in both cases:
GET /SOGo/so/USERNAME/Contacts/personal/CONTACT-UID.vcf/photo HTTP/1.1

If contact contains uploaded photo (as described for first contact), then response has "Content-Type: image/jpeg" and corresponding image.

If contact contains uploaded photo (as described for first contact), then response has "Content-Type: text/plain" and corresponding PHOTO_URI.

"img" HTML element cannot contain "recursive" "src" attribute, it should be equal to PHOTO_URI.