My personal opinion:
I think it is a weaselly action when a forum member removes what he has created and shared before.
He/she could only create it thanks to what the developer of MusicBee and many dozens of forum members have created and contributed to over many years.
If somebody leaves the forum because of some personal frustration or issues: fine.
Also deleting earlier contributions: not fine, and a bit immature.
In my opinion it is perfectly fine to share links to such no-longer-available skins.
They were shared publicly before, and no such thing as copyright applies.
Ideally there would be some repository of older and obsolete plugins and skins.
P.S.
I'm wondering if silvestreccf's entries here:

would not better be removed.
They are leading nowhere anymore.