The 32 node limit within the CloudFormation template available via AWS Marketplace is intended to prevent people from accidentally launching vast numbers of compute nodes. You can override this limit either by downloading the template and adapting it in your text editor or by using the "View/Edit template in Designer" link.
You should change lines 58 and 94 to read:
"MaxValue": "<your desired maximum>"
Using the modified template in CloudFormation will then allow you to supply values up to your desired maximum number of nodes for both the
InitialNodes parameters as appropriate for your use case.
Hope this helps!