Does Vavoom recognize PNG transparency set by image editors like Fireworks?

It should work as long as it's set as an alpha channel <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->.

In that case, no more light blue background needed, right? Should take care of those artifacts we have on e.g. the menu bar.

Yes and yes <!-- s;) --><img src="{SMILIES_PATH}/icon_wink.gif" alt=";)" title="Wink" /><!-- s;) -->.