Hi,
There is a midi/OSC app that supports png image files:
Then use ‘Guided Access’ on your ipad to create kiosk mode.
Another option is hosting the controller in a browser that supports kiosk mode. Node.js can be configured with a browser interface that sends OSC commands to Isadora. Once the functionality is set up, coding images into html should be straight forward. Here is a forum thread describing node.js setup and some alternatives. There is an implementation of node.js for iPad OS.
Example: node.js into Isadora
Best wishes
Russell