Some queries on Power Apps licensing

Here's my insights on this: 

1. Is it possible to consolidate users executing Power Apps on each digital signage into a single user? Or is there a limit to the number of concurrent connections?

Power Apps are licenses per named users, thus only one login per user/license. Besides Power Apps does not have a concurrent license model, which means this license setup would be incompliant anyway. You should license each individual user, not a single 'concurrent user' account. 

2. All the users who only refer to digital signage are required to have a license for Dataverse?

What do you mean? All users will require a Power Apps license. Dataverse is not licensed per user, but per capacity on tenant level. Thus Dataverse is purchased based on capacity consumption, not based on amount of users. 

3. Is it allowed to share one account between the users who execute Apps? Can users of the app share a single account?

From my point of view, no. Power Apps does not have a concurrent license model, but a named user license model. Each user that wants to use the Power App, should be licensed individually. 

You could consider PAYG licensing thru Azure if you think usage of the Power App is low. Then you only pay a license when the user actually uses the app. 

4. Do you know any case studies that using campus apps projected on digital signage?

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I would try posting this article here instead: Find Answers | Microsoft Power Platform Community

Thanks for being part of the community! - jill