My card ideas on the wiki. Looking through my old card ideas, a lot of it was, in hindsight, crap, so that's filtered down quite a bit. I also have a set premise, but it's way too complex to fit in the wordcount requirements of the competition.

(The basic idea was to make it mono-colored, pushing in the opposite direction of Ravnica, then make each color a different type of spellcaster, with very different flavor and mechanics, and something conspicuously missing. For example, red would be an Alchemist, with lots of spells based around combos of opportunity - small-yield combos that're easy to set up, like auras that like to fall off, plus a very high density of linear mechanics; blue would be the D&D wizard with memorization, a morph-like mechanic for 1U without getting a 2/2 out of it; green would be a druid with lots of animal-like creatures, and greatly simplified with instant speed removed entirely; white would be mundane, with nothing magic-flavored whatsoever, and no sorceries, enchantments, or flying (flying replaced by Stealth, "this creature can't be blocked except by scouts and walls", appearing only on scouts)).