Craftec, sure avast! may be redesigned but this release as far as I know is mostly ment to fix bugs and bring some small improvements. Currently we use standard .ICO icons, no PNG or bitmaps and their size is also hardcoded in the program. Antialiasing is not available for these icons.
Lukas, thanks for your promt respond... Yes, I know what is priority when it comes to antivirus or any other security related program and it should be always like that. I was just mentioning new icons, because we all know very well that avast! stands out of any other antivirus utility out there, of course because it's effectivness, but also small part in everything we all have to agree is always graphic appearance. That's all...
Regarding file formats for those icons... nothing is problem. I also use ICO files as well, and in my icon editing utility, normal icon format among all other formats is XP with alpha channel. I just save icon in that format and that's it... of course, it matters if your code engine supports that format or not... but, I just want to say that it's possible. All my icons I made form my desktop were made as XP with alpha channel (32-bit) ICO files.

And see how some of icons I made looks like on my desktop (
Of course I don't keep them on my desktop like that, there are also some variations of the same icon, so this was just for presentation purposes):
