The multiline appearance is not available in the ArcGIS Survey123 web form for an image question with a count-selected constraint.

Workaround

1. in your TYPE field, select image.
2. Add an image question with the name 'photo'.
3. Add 'multiline' to the Appearance Field.
4. Add 'count-selected(.)<2' to the constraint field instead.
5. Save the XLS form and publish the survey

Multiple images are able to be added. If the Integer field is available the XLS form because of referencing to this workflow below, it is not needed for this current workaround. Refer to this article https://support.esri.com/en-us/bug/multiline-appearance-is-not-available-in-the-arcgis-sur-bug-000138683 for instructions.

Steps to Reproduce