I have a couple of suggestions for AISS:

1. The images are rather small.
A scaling solution would be really handy, would also make listview-images obsolete, since you could use any image in small size
I can offer an algorithm to scale GUI-Image-friendly and prepare an example preview if you are interested.

2. For being painted 1:1, they seem to be a bit blurry to me, see the comparism on the image above with the original HD-Rec images.

3. They are also quite pale for my taste, they could need a bit more contrast.

4. The selected state is almost no difference in many of the images, at least the ones I tried. E.g. see the tool bar in the notator window, it is impossible to see which tool is activated.

5. Missing images
For HD-Rec, I would need a couple of images more.
Best is if you would install it and check.
Most missing is something for the waveeditor, the notes, solo/mute buttons for the mixer.

6. The tape-play images are not clear enough for my tast. Compare them with HD-Rec tape-play images.

7. If you have buttons which are very likely to be placed together, like zoom in, zoom out and zoom fit, it is too much to have multiple magnifiers glasses. Looks kind of strings, see the right/bottom edges of HD-Recs windows.

In HD-Rec, I will also add the functionality to "stamp" the images onto a blank button, like Aqua oder simple rectangle. Maybe this could also be an idea for AISS.

I've been playing around with a program called Inkscape to see what's possible with svg images. So far, the images are a little more "cartoony" than I'd like, but I've only just started.

I've successfully built OWB Doduo for AmigaOS4 already, but just with the minimal required changes to get it working at all (using SDL and libfreetype, i.e. no tool bar, AmigaOS4 font implementation, events, window, etc. yet) and I've just started porting it to AmigaOS4.

As there is "only" 12 icon sets in your list will you accept propositions of members that already did one ?