Probably the best registration site about is
www.jetphotos.net/census.
For operator lists, your best bet is
www.speednews.com/lists/lists.shtml.
If you’re after turboprops try
perso.club-internet.fr/f1hgu/turboprop/turboprop.htm.
I’m assuming you already know the
CAA’s G-INFO site and the
FAA’s equivalent.