Can I use a wall tile on the floor?
ONLY IF... the floor surface is well-prepared (1/2" cement board minimum), the tiles have a thick enough body (some wall tiles have a very thin body, and are unsuitable for floor tiles because they're so fragile), and are made up of a material (my favorite is red clay) suitable for compressive loading (your heeled shoes, or high heels), your mortaring work is IMPECCABLE, and your tile-laying technique is excellent.