[Fixed]-Regarding Django philosphy of implementing project as reusable applications

My sugestion is to create a third model, called ArtEvent and make this model points to Art and Event, this way you can create an especific app to manage events and then link everything. For example, when creating a new ArtEvent you redirects the user for the Event app, to enable him to create a new event. Then redirects again to the Art app with the created event, create a new ArtEvent and links those objects.

In future lets suppose that you want to add events to another model, like User, if you follow the same strategy you can separate what is UserEvent specific, and maintain what is common between ArtEvent and UserEvent.