off the top of my head
discussions on the major lines (life, heart, head, others)
discussions of the mounts (mars, luna, fingers, etc)
discussions of unique markings (stars, crosses, squares, and the gazillion interpretations on the various placements of these)
discussions of hand types (air, earth, water, fire, conical, psychic, etc)
discussions of fingers' and thumb characteristics (general meanings as well as digit lengths, bent fingers, other unusual characteristics)
........ just a few ideas .........