CC - indicating if images are modified

The Creative Commons 4.0 legalcode, states in section 3 part a (of each license) that:
“You must[…] indicate if You modified the Licensed Material and retain an indication of any previous modifications”

To help people easily comply with this requirement, something (e.g. tickbox / checkbox, or free text field) could be added to the image copyright metadata to indicate modifications from the original for Creative Commons images. Of course, this doesn’t really matter for No Derivatives licenses.

Link to license if you want to check: