Loading screen cards??

In case Kenji didn't answer your question, that's more about how to get them. If you want to know what a loading screen "card" is:

All Champions have "Splash Art", this is the full size, big art picture that you can view by looking through your Champions list or in the store. After Champion Select when the game is loading (and the League lobby closes and goes into a full-screen with both teams loading the game), you'll notice that each Champion has a smaller portrait; rather than showing the full Splash Art, it has a smaller picture that focuses on the Champion. That is called a loading screen 'card'. Usually the art itself didn't change, but the card's border would change depending on your ranking, or it might have a little "ribbon" near the top-left corner that shows if you have a high Honor or Mastery Ranking.

The latest batch of skins (the PROJECT skins) have "First Strike" Loading Card, so there is some additional graphics to show that you got the skins during the promotional first week. There are a few others that are similar. Some of the previous "legacy" skins now have a different loading card if you bought them before a certain date, because they made the legacy skins available again ("Legacy" skins were supposedly never going to be able to be bought again, but they changed their mind later. Having the special loading card just shows "Hey I had this skin before it was cool")

Hope that clears up your question - let me know if you have any others =3=

Its only appearance is the project skins, you buy them when it's not past 9/15 and you get the loading screen cards. If you are talking about the borders, you get them by earning and climbing in ranked game play. If you are silver+ at the end of a season you get your respective border. Silver, Gold, Platinum, Diamond, Master, and Challenger. You can only play ranked once you hit level 30.