This tutorial is a bit random, but any kind of ideas always come in handy.
I have found the char clouds is a good noise map. Also for diffuse the sludge and acid death textures look nice. Glad someone finally made a video of how it is done. Although it has been common knowledge for a long time.
The demo map has been available since 2011:
Contribute to the wiki (Wiki button at top of page) Considered easy altering of the unit textures?
In reply to DrSuperEvilGamepedia:
Yes, I know it is a bit simple tutorial = (but hey, it is one more tutorial for those who do not know it.
I unfortunately do not know as much as many others, but I will contribute with what I know how to do and possibly they are things that many know =( but well, a video does not hurt anyone =)