Personally, I don't use stickers on the fretboard, some examples are;
dowel rods, tooth pick or skewers for the side, I use abalone dots, there's acrylic rods of various colors, colored coat hangars work well, some primitive builders either wood burn markers or use wood screws, a hole punch on pearloid guitar pics, some have used color pencils-gives a unique look, some have used various decals, and I guess once sealed should last ok.
These are just a few examples, let you imagination run wild, subject has been covered a lot, so if you search, you'll see a lot of pictures of various examples.
some of mine, using dowels, printed, coat hangar and abalone
Those cards look great! How did you do that?
Went on the computer, typed in royal straight flush, printed the image, cut it to fit the fretboard, polyurethane to seal and secure it. Same with the queen of hearts, used an 1/8" piece of plexiglass for the soundboard, printed the queen on photo paper, sprayed it with adhesive, stuck it on the underside facing up.