Hi Anthony,
The discussion (it is at
https://groups.google.com/forum/?fromgroups=#!topic/greasemonkey-dev/pLamU_5hRfE ) links to
http://greasemonkey.devjavu.com/changeset/515 for example, and I found it using the wayback machine at
http://web.archive.org/web/20081214132727/http://greasemonkey.devjavu.com/changeset/515
As you can see, this was committed in a branch, and I don't think that branch ever reached the current git repository.
I'm not sure if the icons in that branch were ever updated by Pak-Kei, but if they were, the format I am searching for (48px) could be in it. For Wikipedia for example, it would not help as much, as they usually have software artwork around 200px pixels high, and often SVG versions.
If you, or someone else (maybe Pak-Kei is on this list?) can still find those images somewhere, would it be appreciated if the SVG version was added to the repository?
In the meanwhile I'll be searching for still higher PNG versions :-) (The highest I have found is the 42px version set as icon for this group, and the version with background from the 2007 conversation).
Greetings,
Môshe van der Sterre