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