In the modern era they are nothing more than place for unique creativity, or perhaps a lack thereof.
Red lines started out having very simple plain patterns such as various sized white boxes or diamonds. Over the years some teams have tried to be more creative and have done a nice job. Here are some examples of red lines that I have found to be creative and unique.
Unfortunately unique is turning into cliche these days as many teams have started to go with their team logo inside the red line. In fact, at this point I wouldn't be surprised if 25 of the 30 teams end up using this concept by 2015.
Finally, I would like to point out some my least favorite red lines in NHL history.