There are many ideas and metaphors on complexity:

Dave Snowden
Cognitive Edge (Snowden)
Sense Making (Snowden)
Dave Pollard
David Gurteen
Karin Cetina
Frijthof Capra

and if you are looking for interesting graphics on the presentation of complex knowledge, try:

Visual Complexity: its rich!

Assessing Complexity
If you need to assess complex processes and their products, this is quite easy to do, as long as you apply a set of principles in line with complexity.