Here's mine for some ideas.
I think if you want a more aggressive look, you need a spoiler and an exhaust. Also with a black car I really think a taillight upgrade is necessary to make them stand out. I think the blackouts just blend in too much. I felt with mine being Magnetic Red that the original taillights just blended away too much as well, which is why I liked the euro tails. Helps to break up all the red.
List of my items are:
ACI rear spoiler
Euro Taillights Red/White with amber bulbs
Chromed Stainless Steel Letter Inserts
Stainless Mesh Screens in Muffler openings
LED license plate lights
Exhaust Filler plate with LED lighting for it as well
Painted license plate surround
It may not be everyones taste but gives you some ideas.