You all don't get it : it's not supposed to be aesthetic, it's about symbols.
The RED of the border evokes passion, conflict, glory and suffering.
The Kaiser's portrait by contrast is white (purity, peace, reflection) but especially BLACK (mystery, fear, distress, death, and in Baresi's case : mourning. Indeed he lost both his parents at a young age).
Combine the two and see what you get. And I won't take "a pissy avatar" or "a Milanese zebra wannabee" for an answer.
Oh screw this I'll do it myself : what you get is a man tortured by a profound inner pain yet aware that it is never too late to better oneself. However his only chance of redemption lies in his resolve to continue this life-or-death combat of his. And that's what the red border represents : see, he wants to unleash his fury against it, he wants to crush this virtual and material cage that keeps him prisoner and cover it with the red of his own blood. Ultimately he wants to cleanse the doors of perception and break on through to the other side.