Due to Licensing of Stock images from Shutter Stock and other Stock site that host the uploaded image cannot be used for Logo purposes even if you have license to use the image
Licensing Restriction from Shutter Stock
https://www.shutterstock.com/licenseRestrictions Part C
RESTRICTIONS ON USE OF VISUAL CONTENT
YOU MAY NOT:
Item 7
Use any Visual Content (in whole or in part) as a trademark, service mark, logo, or other indication of origin, or as part thereof.
Sites such a istock.com have the same policies.
Please take a moment to contact admin for clarification.