Thanks to all for your posts. Yes, the girl is the critical point of the image. Many people I showed the image as WIP told me to let her out of the image to achieve a higher level of realism, but for me personally it was more important to have some living content in it than to make another photorealistic interieur-visualisation. And I tried a lot to make her as realistic as possible for me, but my knowledge about characters and skin ist just too low yet.
About the foam: Its nothing special, no displacementmapping, just a map, which I painted based on an foam-pattern in photoshop and combined it in the transparency-, diffuse-, bump and reflexion channel of a raytrace-material. Here is the map, if someone is interested: http://www.framebox.de/creations/3d/bad/foam_bump.jpg
In the final image I made the edge between foam and bathtub in photoshop a little bit irregular, which could have also been achieved by little geometry noise on this edge.


Otherwise, top job!