I love this fad. I only have a few, but it really impressed me how so much high quality original art was made for phone cards, and guys would pay ¥10000 or whatever for rare ones they wanted.
In the ealier days, before every company was making their own custom cards, anime magazines would make stickers to put over your plain boring cards and make them into Totoro or Nadia cards. Sorta like how they used to pack in inserts for your custom audio cassettes.