Oh neat, I didn't know you could do this in SVG. Very cool! Displacement maps are really useful for achieving a bunch of graphical effects like this.

I used them in WebGL for a couple of different effects in this demo: http://dn.ht/picklecat/

It uses a noise texture to do the background warping: http://dn.ht/picklecat/clouds.jpg

It also uses this image http://dn.ht/picklecat/mesmercatdisplacement.jpg as a displacement map for http://dn.ht/picklecat/mesmercat.png to achieve the fake 3d effect on the cat.