If your interview is tomorrow then you've not much of a chance to make too many changes. Get the basics right in terms of ensuring your shirt's ironed, trousers creased, shoes polished and so on and ensure your hair, hands and nails are clean.
My advice, for what it's worth, is don't spend any more time worrying about what your suit looks like (it's perfectly acceptable) and spend every available minute preparing for the interview itself. What questions are they likely to ask? What particular areas are your strengths that you'll want to steer the conversation towards? What experience/examples from your careeer to date are pertinent to the role and so on?
Of the hundreds of candidates I've interviewed in my own (entirely anonymous) career there isn't one I'd have given a job to based upon the strength of what they wore at the interview although a couple of the more shambolic looking ones have had to work harder to convince me.
In the couple of your posts on here I've read you always come across as a decent, polite and amenable Chap, make sure that comes across in the interview too and you'll do just fine.
Good luck.
