Thank you for your interest in TeamPulse.
Unfortunately at this point it is not possible to add custom images for a persona. However, we already have such feature request in our public Feedback Portal: http://feedback.telerik.com/Project/8/Feedback/Details/597
So I highly encourage you to add one more vote as this will definitely raise the popularity of this feature request.
Also if you have some other ideas for improvement, please do not hesitate to contact us through support channels or directly on our feedback site
the Telerik team