Yeah you can change them, by pressing the icon on the homescreen -> edit -> replace them with the icon in the gallery. You just can't change the icons in the drawer.
But for this theme, it won't change the icons in the drawer automatically, because I would have to code each activity of each app, which is going to take first of all a very long time and second of all, I don't know all of the app's activities. :S
The thing is if I'd pack them into themes, I won't be able to update them as much and as fast; it takes up way too much time and I'm a full time student doing Architecture so. Also, I'd have to open them in eclipse and pack them up again, which if I do that, it may take quite some time. So the way I do it now, i can update my packs within 30 minutes - 1 hour.
I understand that it is more comfortable for people as a theme, but in the end, I'd update it maybe once a month since it's taking an incredible amount of time. :S