If a player is a member, they will have a membership badge in the upper left hand corner of their player card. For this badge, it looks different depending on how long you've been a member or how long you've subscribed for. The levels are just a badge, a badge with one stripe, with two and three and then a badge with three stripes and a star as the highest level. A stripe is added every 6 months, but it doesn't mean that you have to earn them all at once. It just "freezes" if you've suddenly become a non-member. If you are a Non-Member, a star will appear instead of the Membership badge. Moderators have a badge on top of their player card and automatically have a years membership which automatically renew itself. They have been in club penguin since the games launch.
The actual appearance of the card has changed. If an item fails to load, an X appears in that slot. This is where the user can change their penguin's attire/appearance. Users can also find out how many coins they have.
Only famous penguins, puffles (while being walked) and transformations have been known to have poses on their player cards, and if a player has a bait item, their player card might change into a pose.