This is a fun effect to try with filters in PhotoShop or PaintShop Pro.
Thanks to Phil for reminding me of this Flaming Pear filter called "Veins".
I took a Mardi Gras photo (but try it on lots of different photos for really
wild effects) and I applied Veins, then Simple Filters' "Top Left Mirror",
I tweaked the contrast/brightness and embossed a bit, then added sandstone
texture.