That's a difficult question.  I've worked in a "specialty" video store in Toronto, Canada for 17 years (the last 4 as manager).  I don't think there is any "type" of person that watches foreign and indie films.  I didn't think I would like "serious" films when I was a kid (I had seen over a hundred horror films before I was 11), but when I stumbled on CITIZEN KANE on television one Saturday night, I was transformed!  I recently hired a 17 year old young man.  I asked him, out of the blue, "So what was your epiphany?".  He didn't even bat an eye, or ask me to explain myself, he just blurted out, "Definitely...2001: A Space Odyssey, when I was 12!"  I guess what I'm saying is, you can't really market the type of store you're talking about.  Save on the advertising money, put it into your rental library and...don't worry.  If your product is "good" the customer's will find you.