Unfortunately, all the examples I am aware of are proprietary.
Constellation contracts are one of a number of intermediate to advanced modelling techniques that includes intensional domain modelling, implicative choices, ephemeral post-condition contracts, stable-data/dynamic-workflow separation. To be honest most of this stuff is still communicated word-of-mouth by those engineers lucky enough to have had the chance to work on DAML projects of sufficient complexity to require these techniques. At some point we will need to prepare more formal training around these, but that work hasn’t been done yet.
To be fair, the vast majority of DAML projects do not require these techniques; almost by definition, the sort of explicatory problems used for sample code are not complex enough to require them. In the meantime, if you run into a problem that needs these techniques, this forum is a good place to ask about the problem — they are much easier to explain in the context of a concrete problem then in the abstract (ie. I discuss intensional modelling here: Indicate list of OR signatories)