There are several things you can do to create a great poster. Here are a few points to consider:
First, I would have an image that prominently displays the new blackberry phone, so that people will know what the product is. Too often, the product is not display as it is eclipsed by models or other elements in the poster. In connection to this, several pictures might not be a bad idea as long as the phone is prominently displayed.
Second, you probably cannot show all the specifications of the phone in a poster with effectiveness. People just walk by posters and so you have a few seconds at best. So, you will have to choose what technical aspects to highlight. For example, you might want to prominently display the 4G features. This will show people that it is much faster than the iphone. The other technical aspects can be written in smaller print for people who want to learn more.
Third, the company's brand must also come out. As much as you want to sell a phone, you want to sell the company as well.