currently it only supports 8x8 tiles, HOWEVER, it will import your tile spritesheet and slice it into 8x8 tiles for you - so you'd import them, then use the Designer tool for the actor, set the actor size to 16x16 and pick the 8x8 tiles that make up your 16x16 sprite (i know, it's a bit confusing, i may work on a better solution for this, but for now, that's how it's done)