There is no any bindings available for button and a image widget ,i guess can be done but you need to have
the storage location for Thingworx media entities (if there are static images) in datatable or make repository to store the images and then access them,
for instance as ServerUrl+"MediaEntities/ImageName" (if they are thingworx media and not repository created media /files) .
The next step would be to have service which will loop through all
datatable entries , the result of this service will be url , but it should be random Url , rand(imageUrl) .
Then Bind the result to textbox , then bind the textbox text value to image widget as Source Url , this
service will invoke on Button Click
Let me know if it sounds good to start ..!