I realize you have already submitted your posters, but I wanted to take the opportunity to give you some design ideas to consider.
When you are designing a poster, make sure you consider how to best use all of the principles, actions, and tools we've covered to date. For example, when laying out your poster, you don't need to stick with a static rectangular format. You can experiment with introducing different shapes, diagonals, and lines to create a dynamic rather than static layout. Also, you can use contrast to focus the viewer's attention.
Likewise, you don't need to use black type on a white background, even if the poster is for instructional purposes. Here are some examples of interesting posters. I hope you carefully examine these before making corrections to your poster for final submission.