Have you checked that you can publish those photos on instagram?

4. You represent and warrant that: (i) you own the Content posted by you on or through the Service or otherwise have the right to grant the rights and licenses set forth in these Terms of Use;

1. Instagram does not claim ownership of any Content that you post on or through the Service. Instead, you hereby grant to Instagram a non-exclusive, fully paid and royalty-free, transferable, sub-licensable, worldwide license to use the Content that you post on or through the Service, subject to the Service's Privacy Policy, available here http://instagram.com/legal/privacy/, including but not limited to sections 3 ("Sharing of Your Information"), 4 ("How We Store Your Information"), and 5 ("Your Choices About Your Information").

https://help.instagram.com/478745558852511

The rights they request may be a subset of those already granted by the copyright author in the chosen license... but I wouldn't be surprised if there was actually a legal conflict of their terms, which would preclude third parties from posting them there (eg. instagram dropping the link to the license).

Best