Did these using the same water-marbling technique I mentioned in an earlier post some time ago. I actually really like how they turned out this time though. Excuse the little ugly stray marks; I wasn't able to scrub those off too well.
I was actually inspired to do these when I was distracted by one of those Facebook ads on the side of the screen while I was supposed to be doing homework. Typical me. The tutorial's here (seriously, Youtube has tutorials for everything).