Like Chelonian before it, Scutum is magnetized for in-game use and ease of painting.
I also spent some time this morning figuring out my banner situation. After playing with several banners I had around the house and test-fitting a few from bits sellers, I settled on using a large, raggedy, WFB Orc banner for my trench-line "command squad" and hacking up the smaller, Space Marine Command Squad banners in a similar fashion for the subordinate squads. The top of the Astartes banners ended abruptly, so I topped 'em off with skulls. Unfortunately, this made the skull atop the Orc banner look plain, so I hacked it off and added a scarred helmet that's likely to be a bright, shining yellow when I paint it.
Next up: Two Chaos Vindicators. I've already got the hull assembly completed and have modified the driver's windows. Everything else is just fiddly detail work to make it look Iron Warriors-y.