Manual 4 Speed? Serious? I think you MUST me mean 5 speed yes?
Anyways, the interior of your car should be unique. Honestly I love custom fiber glass molding on the interior of a car. That's expensive unless you have the equipment and the know-how to do that yourself though.
I highly suggest you get some nice, comfortable racing seats. The steering wheel I want is the SRS JDM Accord Type-R black leather wheel. Can't go wrong with that, unless you don't want to spend $800 on a steering wheel. Definitely get a short shift kit and a new shift boot and knob. Get those reverse indiglo gauges, those are super tight.
Another way to go is like super luxury. Get the after market leather upholstery for like the whole interior of the car. Get a really clear sound system with a GPS system and 7" monitor built into the dash. Maybe a wood finish dash would be good for that.
I dunno, really this is the kind of thing you should be able to figure out yourself. Of course, I'm a fan of modifying under the hood and the suspension before doing the interior at all.
