I started to use ZedGraph a few weeks ago and find it very usefull and are impressed of the capabilitie.
Intensity graphs (matrix of X-Y where the value (Z) in the matrix is plotted in a color representing its value) is used extensively in my work. This was solved by making a bitmap and inserting it as an imageobject.
Intensity graphs needs a "Z-axis" representing the value of each color and worked a little bit to implement this ino the existing ZedGraph code, by a new class called Z-axis. Unfortuenately some changes had to be done in existing code to use the Z-axis class.
I am contiuing to develop this, but I am probably not able to follow your quality of programming. Have you ever considdered to implement this? Are you interresting in the code, I will send it. See the attached file fore example output.