So I have left the labeling up to each customer - and their solutions have been very creative. I think the best solution is from RainFallCrafts who sells these handmade markers designed specifically to work with Grace's Cases on Etsy. She offers them in a variety of colors and numbers or you can request a custom set. To protect your needles she has avoided using metal crimps so you don't have to worry about them scratching. Just Brilliant!
I plan to use mine both in my case and in my projects. Since they are easily removed I will add a marker to my WIPs to indicate what size needle I am using, and then if I get in a pinch and need an extra stitch marker I can use it for that as well! Again, just brilliant!