How to procedurally generate a veiny skin material? I want to make a Cycles material that looks like these images:







The material should be slightly translucent and have thin veins underneath it.

I understand how to make the translucency, but the veins are giving me trouble. Is this something that can be made procedurally in Cycles, or will I need to make a vein texture in GIMP and somehow combine it with a skin material?
You can generate a skin material with veins like this using wave textures, musgrave texture, and translucent materials. The waves are distorted to get the meandering of veins. Different wave textures are combined with different orientations to get the veins running in different directions. The musgrave textures is used to make the veins appear and disappear in different areas.

The bright spot is from a lamp below the 'skin' illustrating the translucency.





This material is generated as shown below:





A good reference for generating veins in skin is at https://gooseberry.blender.org/shading-kenny-the-caterpillar/ 



The blend file: