Adding A Space Marine Vexilla To Your Force

So far I have really just been making and arming my War Hounds in a way that I think they would be armed based on fluff and what seemed to fit.
Then earlier this week I came across two simple tools that will enable anyone to properly arm their Legion to actually field a force.
One of the added extras I found was the Vexilla, a Legion-specific banner that lets you re-roll morale tests - every little bit helps, right?
I really like the look of Marines with banners - in fact I'd love to have a whole Chapter flying them. The original fluff says each marine carried a banner in their backpack, so why not use the fluff to make something cool. 

Here's the first of the Vexillas which will be carried by each of my War Hounds squads. What do you think?

Do you use the Vexilla in combat? Have you found it handy? What's the best way to use it?