The label will have to portray the image the brewery wants it to portray. The field is wide open after that. I have seen awesome labels on all kinds of beer, in all kinds of styles, but there are a few that just don't do it for me. And the beer might be excellent, but I'm afraid the label often gives it a bad impression if not done right. But others may very much enjoy those same labels I don't.
Generally I don't care for a label to be too "busy". OTOH, I like reading labels, so the more stuff you can print on there to read while I'm drinking, the better. I like to know more about the brewery or the beer, so that is always good.
Avant garde design is usually not my preference, but if that is the style the brewery is trying to push, then it might work for them.
Lots of breweries do their labels in similar styles across all of their beers, and some use a very simple logo design that is easy to notice among lots of beers on the shelf. Case in point, Bells Beers.
Flying Dog uses the same artwork for their beers, but the images are very different at first glance IMO. However, once you see the label, you know who's it is.
I'd get to know what the brewery's attitude about their beers is, or the attitude they wish to present to the customer. I mean, lots of beers are very similar tasting, but the label can actually be the bit that gives the beer the right appearance, not the beer itself (although a bad beer will doom it, and an excellent beer can often sell itself regardless of the label).