Looks okay, but where is the smoke ring?
Just inside the edges of the dry rub? I dunno, I can see it. Also remember this was only smoked for 4.5 hours, I get a more pronounced smoke ring when I am smoking regular brisket for 12-15 hours.
You typically only get those ridiculously thick, bright red smoke rings if your fuel source is wood (most smokers just use wood for flavour), or you are adding enhancers.