Auto-generated background images! Yeay.

The code for that is really simple-
(div style="background: url('http://tacosareawesome.com/bg/255/0/0/50/image.png');")taco(/div)
You'll see "bg/255/0/0/50/image.png"... That's formatted as bg/r/g/b/a/image.png
where r=red (0-255), b=blue (0-255), and g=green (0-255). A is alpha, which is 0-100 where 100 is opaque.