Hi @vpn1 ,
You need to add the image_picker field in the schema in quotes.liquid same as below image and fetch the field in the template.
If you don't know coding then please accept my collaborator request, I will do it and explain you how to use it.
If you are using testimonial app then there will be an option already otherwise,
If you want to add image without app then you have to add schema in your testimonial code.
Please Refer below link