I am fine with the idea of the tileset having multiple themes, but I don't think those shiny bricks are the ideal solution. The nature/castle theme is a fairly simple concept, and has been done many times, particularly in JJ1. If I wanted to make one of those levels I would probably use Exoticus or Nature's Ruins. I second the vote for the bricks not being a good addition to the tileset, although I also have nothing against them on their on own.