Your question makes me think of my friend's apartment... though he's into mid-century horror and sci-fi kitsch and not punk, the dilemma is similar. i'll share some of the ideas he used to turn his unique interests into a classy place with a lot of personality...

1) One of the single biggest things you can do to avoid the "bachelor pad" or dorm room look is make sure everything displayed on the wall is framed or appealingly mounted. Framing and mounting can be expensive, but doesn't have to be ... my friend shopped at thrift stores for cool looking, uber-elegant old frames, then cut them down himself to fit his artwork (he has quite a few Mark Ryden prints and some prints of paintings used for the old '60s "Night Gallery" TV series). If you have a lot of cool posters but not a lot of wall space, an idea that might come in handy: find a really cool poster frame and occasionally rotate your collection into it vs. trying to frame and display many posters without appropriate space to do so.

2) For smaller collectibles, a lighted curio cabinet is a great way to display them. Almost any item gains dignity when placed in a curio cabinet :-) Sometimes you can find some really nice ones at stores' "going out of business" sales where they are selling store fixtures, often for a very low price. You might chance upon one that is really unique, but it's also possible to add interest to a boring one with a little ingenuity, paint and varnish. If you customize, I wouldn't hesitate to give it a "punk" look ... the trick is to take aspects of the punk aesthetic and use them in a way that says "art" rather than "accident."

3) If you can, paint your walls a color other that white or "landlord beige." I think color on the walls always gives an artistic flair to any home, and it's one of the least expensive ways to give a dramatic facelift to your decor. Color is also a great way of saying "this is my home, and not just a place I'm camping for a year or two." My friend painted his living room a deep red, which creates a great atmosphere for his dark collectibles.

4) Have some fun with unique light fixtures ... my friend replaced his landlord's standard issue Home Depot lighting fixture with a faux antique brass chandelier that has monkey's swinging out to hold the sconces. Very cool, and it was under $150 (not sure where he bought it). Having lighting fixtures that echo the overall theme of the room is a strong way to reinforce that you've made design choices vs. a situation where the things that express who you are appear to just be camping in an otherwise standard-issue room. You can also have some fun with unique switchplates--my friend replaced the plastic switchplates in his apartment to nice looking antique brass ones.

5) WIndow treatments should be cohesive with the overall vibe of the room. My friend chose to make some brocade tieback curtains that give a Victorian mansion-like feel to the living room (and also the bedroom). This was kind of an expensive project--even though he made them himself the fabric cost quite a bit--but you can get a cohesive feel with something simpler that can be bought at Target or Bed Bath and Beyond and/or buy some curtains and customize them a bit. And window treatments can be something other than curtains...again, don't hesitate to express your creativity and personality! You can find a lot of basic window treatment ideas on many home decorating sites online, and those can be great starting points for inspiration.

6) The kitchen and bathroom are a great places to have fun with more witty and informal displays of collectibles and kitsch. :-)

Overall, my biggest suggestion on this is to fully commit to bringing a cohesive yet eclectic expression of yourself, your tastes and your interests. Express yourself artfully in every aspect of your decor, and you'll have a really cool house.

All my suggestions here are based on personal opinion--my friend's apartment and a bit of my own approach to home decor. For more points of view, you might want to check out some of the links in my sources list.

Good luck, and have fun!