Not sure this could be an easy fix for v3.0. If not, I'll add it to v3.1 skin wishlist:
Currently if a skin is using a custom node icon override, all other default icons need to be supplied in skin files even though they will be available from MB.
Try any Pastels or Dark-Fine Tuned skin.
Would it be possible the skin doesn't have to supply the same default icons for Bookmark, Podcast, Audiobooks, Radio, inbox, Video, History, Upcoming Release nodes?
If it doesn't supply those, playlist, auto-dj, now playing icons won't respect their icon overrides. I found that podcast icon needs to be added to make them work. But then all other nodes don't show any icons.