Hey Luke,
Another really nice way to really draw attention to something in the app is by using an Answer Exception. An answer exception is trigged based of the answer of a question, but you could use a little conditional logic in combination with the exception. You will need to use something like a radio button to trigger the answer exception but a radio button allows you to have just a single option to pick from.
You could create a Radio Button that includes your Warning message and use the option "Photo not included". Then using conditional logic, IF Photo Question is not answered THEN Radio button is set to "Photo not included" which in turn would also trigger the answer exception. You could even hide the radio button question when the photo question is answered at the same time.
Would look something like this in the app:

Thank you
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Ian Chamberlain
Solutions Architect
TrueContext
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