Planar Conflict - Card Backs

I ran into a bit of a problem while working on card backs for the Infernal decks. Basically it boils down to this: Vassals need to stay face down until they are revealed during combat. As a creature, Vassals are single bordered on the back, but so are Shields and Terrain; in addition, flying Shields must reveal their contents. So how could I design the card backs to reveal some cards but not others?

I did a small reworking of the single bordered card backs and here's what I came up with as my final solution...

First, here's the standard card backs for Vassals, which remain face down. It simply says "Planar Conflict" below the Guardians logo.

Next is the card back for flying Vassals, represented by the same wing icon used on the front of the cards. These cards get revealed because they are flying.

Then we have Shields, which are represented with a new Shield icon.

Since Planar cards are both Stronghold and Terrain, the backsides of Planar cards will simply be rubble.

Finally, the double bordered cards, which are Glyphs, Relics, and Events.