Python - 196 chars

Creates a Sierpinski triangle.

import Image as I
t=1000
a=I.new('RGB',(t,t),"black")
p=a.load()
def r(x,y):return(x*16)&(y*16)
for i in range(a.size[0]):
 for j in range(a.size[1]):m=r(i,j);p[i,j]=(m,m,m)
a.save('s.png','PNG')