In celebration of 2000 pages, I'd like to share a good example of incorporating nonwhite elements into a traditionally very white setting. A fanartist by the name of @Cosmiart (that's the name of her twitter, tumblr, and insta) draws a lot of excellent A Song of Ice and Fire fanart. In it, she adds a lot of central and east asian elements to the North's clothing and draws most Northerners as slightly darker than their Southern counterparts, but they're all still recognizably white.
She said that she did this because she thought it would be more fun to draw some variety rather than just drawing the same western European clothes for all of the regions in Westeros, and that it helps to show that the Northerners are indeed ethnically and culturally different from the Southerners like they are in the books. I think the way that she approached it is a really good way of a fan adding ethnic and cultural diversity into a work and making it look natural rather than stupid, forced, or virtue-signaling.