Several different tattoo alerts for the Whitebeard Pirates, and I do think it's interesting that Ace is the one that put WB's mark on his back.
From a logistics standpoint, it's easier for Oda to show off all these tattoos without having half of Whitebeard's crew running around without their shirts on, but in-universe what you chose to wear on your back--and who you show your back to--has a heavy association with a person's honor.
Whitebeard and Zoro are both noted to not have wounds on their back, with back wounds specifically mentioned on being shameful. Ace and Roger both are known for refusing to back down or run away when insulted. Later in Wano, the Red Scabbards also mark their backs with the Kozuki family crest as a sign of their loyalty.
When Ace eventually dies, it's with his back to Akainu, the mark of his loyalty to Whitebeard completely obliterated in service of his sacrifice to Luffy.