I've been uploading a lot of Touhou project's traditional art lately, especially from the artists maa_(forsythia1729), beluo77 and d-m_(dii_emu)
although I have my reasons for being cautious about uploading such images.
especially with grayscale/monochrome images, sometimes they approve, sometimes they don't, reason, I don't know, I'd like to think that the unapproved images were really low quality, but I often doubt it, I mean, I'm aware that taking the wrong picture can ruin a good traditional drawing, but sometimes I feel that it is criticized too harshly.
it's as if you are held to such a high standard that sometimes it's not worth it, every imperfection subtracts points, whether it's a small wrinkle in the paper, a shadow, a slant when taking a photo or even a pencil on the edge. you know, a lot of things to consider, very difficult.
so if you are planning to upload traditional style images, I recommend that they be colored, don't worry if the colors are a little muffed, if the image is colored it has a much better chance of being approved, a grayscale traditional style drawing I feel it is taken as a simple sketch.
or maybe I am being too bland and i uploading low quality images.
that's what I can say from my own experience.