I'm sure that you're looking at a lot more airflow now with nothing behind that big fan.
I wouldn't worry about painting the inside yet, but I'd try to get a theme going with the existing cables first. I'd lose the green sleeving for some black, the green stands out way too much. I'd also get rid of the green SATA cables for some black ones too. You might find my taste to be a little bland though, I just like things clean and simple.