Hey, there -- I did this image in RayDream a LONG time ago (back when I was AzChip), but I remembered that it had something like what you're describing. Now, I just have to remember what I did. As I recall, the brick texture is a BMP and I added a layer of gunk using a mix of the brick with a dark greenish black color using teh Marble operator to get those long moldy areas along the bricks. I also used the marble operator in the specularity channels (can't remember what they were called in RayDream, but it's like the highlight and shininess in Carrara) to get some varying reflectivity to the brick to give it a wet look. Hope that's helpful. - Dex