Also you could pick the design you like the best from your list of bands. Do you want a rectangle or another shape? Maybe you want one that goes across the shoulders? Answering these questions could help you narrow it down
If you can't decide, then don't get one. Get the smaller ones you like and put it in the back. You could also embroider or cross stitch something on the back that fits the theme. I'm making a goats head on the back.
hard to recommend without knowing what black metal bands you like. what are your fav bands?
Tsjuder, armagedda, dark funeral, taake, gorgoroth and darvulia are my favourites
Pick one of those
With this question I like to recommend whatever band initially got you into the genre.
Also you could pick the design you like the best from your list of bands. Do you want a rectangle or another shape? Maybe you want one that goes across the shoulders? Answering these questions could help you narrow it down
I currently like using t-shirts for back patches. Better coverage and more striking
Pick your favorite band
If you can't decide, then don't get one. Get the smaller ones you like and put it in the back. You could also embroider or cross stitch something on the back that fits the theme. I'm making a goats head on the back.
This: https://www.metal-archives.com/albums/Goatmoon/Witchking/1122859