With the Iron warriors we also need the Imperial fists! Make sure to cast your votes brothers! Not convinced yet? take a look at : http://wh40k.lexicanum.com/wiki/Imperial_Fists
Raven Guard and their "shadow" tactics would def be a nice adition to chose from but the Imperial Fists and their story's and customs just feel right for me, to bad some just see them as yellow smurfmarines.
I look at it more as being about not just having opposites of each other on Space marines and Chaos. At the same time I don't want Raven Guard because they are so similar to Night Lords. I wouldn't want World Eaters to start cause of Blood Angels parallels or I guess because of similarities to Space Wolves. Salamanders or Iron Hands would be my preferred choice but ultimately its up to them. Salamanders prob not cause they are green like DA. Ultimately we'll have all the Founders so it really doesn't matter too much
Battle Brothers! do not forget to cast thy vote! This is our Darkest hour and every vote can be the Golden vote for us! May the Light of the Emperor shine upon our path and show us the way to the Fields of Glory on Arkhona! "Primarch-Progenitor, to your glory and the glory of him on earth!"
Well found one with google in a "online poster maker" saying : Keep Calm and Fortify Terra And just used that one to make new ones currently looking for more inspiration haha