For quite a while, Agua by David Lanham has been my favorite icon set. A while back it was updated for Leopard with 512×512 icons, slight restyling and additional Leopard-specific icons (downloads folder, Time Machine drive, etc.). However, because these folders were angled (rather than front-on like Apple’s Leopard folders) they looked super messed-up in CoverFlow. Now (well, a bit back) David Lanham has updated the folders so they are front on (he also added a couple drive icons and another alternate downloads folder) and look decent in CoverFlow. If you use the Agua Leopard icons or are looking for an alternative to the regular icons in Leopard, check out the twice updated Agua icons.
If you were wondering, I do hope to make Desktop Extras a regular feature (I made a banner for it and everything). I plan to cover things such as icons, wallpapers, dock styles and whatnot. As always, if you have suggestions or questions for Desktop Extras (or any other feature) give me a shout in the comments or you can email me (see the contact page).