“Could an in-home digital network have ads or is that sacred territory?”
Any in-house digital network can have ads. What you have to decide though, is what your end goal might be. Depending on what your use case for your signage network is, advertising might be something that is completely misplaced. On the other hand, it could be used as a revenue stream or something used to push traffic to partners and vendors in and around your organization. One would have to be careful to consider the ramifications and the potential content that may arise from people wanting to advertise. There may also be content that isn’t sized correctly, causing resolution issues, which makes the signage look terrible. With that in mind, a content policy or set of guidelines would be important to create and share with all potential advertising partners, along with a set of content standards to make sure the message is relevant, on brand, and suits/fits the signage network.