Well, as a former recruiter, I can confirm that grunge style is not exactly corporate wear. So you may need to save most of your grungy items for your leisure time and instead do your best to fit in with the style and values of the organization you are going to work for and represent.
Try to get information about how your future colleagues dress. What did you notice at the job interview? Is it possible to wait near the building when people are leaving, so that you can get an idea of their dress code? Or you can simply call and ask. (That will often be appreciated.)
In many offices, jeans are allowed, but this does not mean any kind of jeans. Unless you know for sure that people at your future workplace dress very casually, I recommend you to avoid ripped jeans (ripped anything, actually).
Black jeans, T-shirts, sweaters, jackets and other black items will likely be OK, provided they are without holes etc. As for band T-shirts / graphic T-shirts, make sure that the texts and motives are not in conflict with your employer's values or getting too much attention. (You, or at least your employer, will likely want the main focus to be on the organization's products or services. This is especially important if you are going to have contact with costumers/clients. If you have a more "invisible" job, however, you will often be allowed to dress more casually.)
Are checked flannel shirts (i.e. red & black, or green & black) part of your grunge style? I guess they will be possible to wear at work, maybe styled a little differently.
A final warning: Being unkempt is often a key element of grunge style. However, at most workplaces, unkempt hair, nails, etc. are not appreciated. So, dependent on your present preferences, you may need to adjust to a more groomed look. However, you are not expected to look girly, cute, ladylike or glamorous. Aiming to look, and be, clean and well-groomed goes a long way. But you did know this already, didn't you?
Best wishes for your new job and new style!