Ok first off I do not claim to know anything about themes, or the themeing process in general. Take this info into consideration before answering.
Secondly, I LOVE bgills invernito theme except for the app icons, this actually goes for a lot of themes. I think they look pretty pimp on the home screen, but hate the way they look once you pull open the app drawer and they just pop out at you and say, "looky here I don't match any of the other icons." Themeing the app itself is completely fine, just not the icon. Don't get me wrong, I'm not trying to bash the themers for what they do, because I think they do a fantastic job. Just my little gripe.
So question being is; how do I change them? Is there a way? Should I just request that bgill maybe have an extra .zip for an icon pack? Does anyone agreeth with me? Thank you for your time.