Texture Tips: If scanning, scan using Black & White Mode with a DPI of 300-600 as a PNG or JPG. Your smartphone camera is also an excellent tool for digitizing your textures, just be sure to take them in a well-lit area and directly above the piece, avoiding shadows. You’ll then want to convert the photo to B&W. Your textures might need some adjustments using Levels or Curves in Photoshop.
Photoshop: Once you are satisfied with your adjustments you can change the mode to Bitmap and save out as a TIFF, which you can bring into Illustrator and apply any color to them. They can be applied directly or masked out, however you’d like to work with them!
Illustrator: You can work with a color photo or converted B&W image, you’ll get different results so maybe try both! Once placed in AI, select Image Trace and open the Image Trace Panel. Here you can play around with the various drop-downs and settings to achieve the texture that you are looking for. A quick tip would be to select Black and White Mode and check the Ignore White. From here you can expand and delete any extras. Which ever mode you go with, you’ll want to turn on Ignore White to have a transparent background.