Search through the SDK document for "_metatype"...
Hi Neil,
You can't change the icon in the Resources window, but for instructions on how to change the icon in the Toolbox, search the SDK document for "Icons for Toolbox Items".
Please consider (if you've not done this for 7.0 already) making metatype a read/write attribute somehow (or making the 'background' property accessible for writing).
As well, please consider extending icon support to the Resource and Project Browser windows.
David