You can use PeterK's awesome icon.library to put the iconset of ClassicWB AdvSp (you can copy these icons from that archive).
In general ECS chipset is rather slow with 16 colors, and the nice iconset from AdvSp or 3.9 looks rather poor with anything less than 16 colors.
I have the exactly opposite... which means an custom ClassicWB 3.9 installation which runs on 8 colors based on MWB palette, on SuperPlus and it's
really fast and responsive on my ACA630@30.