It seems to me that the procedural textures aren't render engine dependant, I guess I'm wrong. Does anyone know why this is?
Is there anyway to get a procedural marble texture into cycles? (or simulate it in some way?)
The Wave Texture node has Distortion, Detail and Detail Scale controls that can be used to generate results like the Marble texture.
The textures are different because the whole shading system is different, we decided to redesign it entirely. Some texturing features from Blender internal are still missing because we haven't had time to add them back, we can't reuse the code directly because everything needs to be reimplemented for Cycles to work on the CPU, GPU and Open Shading Language.
In the Cycles rendering engine, both the Marble and Wood procedural textures are merged into a single texture known as 'Wave'.
You can use the Distortion and Detail settings to achieve the old Marbles look. One setup to achieve a look like the old Blender-Internal Marble texture is:
This returns a texture that looks like: