If your app lets the user share images, consider implementing the possibility for them to add an alt text for the image, so it can be used as an accessibility label when consumed by other users. Twitter or Slack have nice flows for doing this.
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Some recommendations for improving your accessibility labels: don't add the element type, avoid redundancy and verbosity, localize... @MobileA11y has an excellent blog post on it: https://mobilea11y.com/blog/writing-great-labels/ @jordyn2493 has a great video too: https://developer.apple.com/videos/play/wwdc2019/254/
Manual testing is crucial. And therefore, reducing friction to let you start your testing process can be a huge help. Selecting some accessibility shortcuts will do that, putting most of iOS' accessibility features at a triple-click of a button.
When configuring a largeContentImage or adjustsImageSizeForAccessibilityContentSizeCategory, it is important to use a pdf asset and preserve the vector data so the icons are crisp at any size.
