Hi Sam Tran,
Thanks for contacting Syncfusion Support.
Based on your shared details we have prepared a Kanban sample with Dialog edit mode with Template. Here we have rendered the image as base64 string from byte array data as per requirement. But we can able to show the image in Dialog Edit Template mode. Please find the below sample for more information.
Also we could not download or see the image that you have shared. So if possible could you please share the image once again?
Please check our shared sample and If the provided information and sample does not meet your requirement or if we misunderstood your query, please get back to us with more information, so that it will help us to provide the solution at earliest.
Regards,
Arun P.