Maybe adding some "vibrant light" translucency?

Did you try adding the "Visual Effects View" as the background and adding some slight translucency?

It's really simple to add it, but it makes the app look more "fancy"...

Just drag & drop the "Visual Effects View" to the background and set up the effects in the Attributes Inspector.

If you also want to try out some "fancy" titlebar, you could for example try out the effect like in the Reminders app's sidebar by checking "full size content view" in the Attributes Inspector for your window and adding something like this to it's class:

```
class WindowController: NSWindowController {

override func windowDidLoad() {
super.windowDidLoad()

window?.titleVisibility = .hidden
window?.titlebarAppearsTransparent = true
}
}
```

And you get something like this: