New: pick a card as your deck's icon

Decks used to show a plain color-coded circle wherever they appeared - on the deck list, in the deck detail view, everywhere. That still works fine as a quick color reference, but it made every deck look the same at a glance. Now you can pick a card to represent your deck instead. When adding or editing a deck, search for any card by name and its artwork becomes the deck's icon. Your deck's colors still show up as a small badge in the corner, so you don't lose that information either. Didn't pick a card? No problem - decks without one still show the color circle exactly as before, so nothing changes unless you want it to.