There isn't much i have done for the inside except for sound. I have the JVC KD-LH3100 head unit. For speakers i have kicker 6.5 components with the 1in tweeters. I also have 5x7's in the back seat. My sub is a JL Audio 10 with a Kicker Impulse 300 watt amp. Thats it for sound.
Here is a pic of my head unit. I like it. It has alot of stuff u can do to it like your EQ. I bought that EQ on the bottom of the head unit to customize the sound better but the unit does a pretty good job. So i am not even using the EQ. I guess i have it just for show.
Here is an inside pic from the trunk. One day I will be havein all the pods and carbon fiber dash kits and racing seats. One day
This is my JL Audio 10 sub. I hits pretty had. Especially since my car is an hatch back.
This is my sub again but better pic of my amp. Its a Kicker Impulse 353xi.