The banner is just great ! A fine piece of artwork there, Binôme ! Since I've seen the missing arm, I know it's good ! But this is true, the background is not ideal...
And even though it would maybe distract from the banner, I find the marine a little too...normal...some improvements on his armor would have been nice, I think...He's the standard-bearer...he is an important part of the Chapter ! (or the company, at least)
Again, I love the banner and the minis well painted but my advice is avoid static grass and a green base (I may seem a little anal here but I just don't like it and it and I think it distracts from the mini) Also I can't see the missing arm detail too well with the universe behind it.
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