Yes, I use the offset quite a lot too for different reasons. And the colors of a fractal to drive displacement, not the displacement itself. Is there any particular reason why you use a png? I always use tiff, but it may be just a personal choice.
Update: some overlap again (sigh). That's the problem when using more than one vdisp in line. I didn't yet get that into one non-overlapping vector, and even if I did, the vector displacement only displaces one way, afaik. The razorbills are old objects and need updating, btw.