You should see many more older releases under the "All Releases" menu. Mine go back all the way to 17.2. If you don't see them, it might mean that your cco isn't properly tied to the contract for your 1100s. web-help@cisco.com might be able to help you with that.
I'd also like you to reconsider running 17.5 since that was just a short lived release that was meant to deliver new features. 17.6.5 is marked as a Suggested Release by Cisco. You probably want to start planning for a Vmanage upgrade too.