I'm quite fond of Mystic Mines, but agree with its one review that it doesn't really offer too many possibilities, despite being pretty. CrysilisV is supposed to resemble a mine, but clearly not of the same style. I'm in favor of us getting another mine tileset -- minecarts are a gaming staple I adore, even though they're not easily translatable into JJ2 -- but I feel this one needs a little more fleshing out. Right now its gimmicks are lava and crystals, and we've seen both of those before, here and in other games. The backlit effect is a good idea that we don't see much of, but I do recommend adopting Stijn's Lucky Luke suggestion and incorporating lots of wooden beams, because mines are full of those and yet we haven't gotten that detail in tilesets yet at all.
(I'm concerned that the proposed layer 5 uses too many circles... compare.)