The characters I created for the Donzalo books are not based on real people. Not really — one can not say 'this character is that real-life individual' or anything of that sort. This is not to say that certain characteristics are not borrowed from public figures, historical personages, even characters from fiction, and, occasionally, actual acquaintances.
The ambassador Lord Doufan, for example, started out with a bit of Henry Kissinger in him (though he is certainly much better with a sword!). Along the way, I think a smidgen of Red Reddington got into the mix. That would be more as a 'type' than an individual.
But it brings me to something else, the physical appearance of the characters. I do find it useful to be able to visualize them and choose pictures that help me with this. Doufan does look rather like James Spader in my mind. Similarly, the minstrel/spy Guesare resembles Kenneth Branagh. For that matter, Princess Lomela would look much like Branagh's ex-wife, Emma Thompson. Both of these would be when they were somewhat younger!
Similarly, I envisioned celebrity cook Nigella Lawson for the evil sorceress Nosana. I am sure Nigella does not cast spells and poison lovers, but it gave me an image. Others were not celebrities at all, but random people I found online. Lady Fachalana draws her looks from a Latina porn actress who shall remain nameless (a bit ironic for the rather uptight and virginal swordswoman).
And some, inevitably, did draw from people I know personally. Prince Modareth resembles a poet with whom I am acquainted; his wife, a former girlfriend of mine.
And Donzalo himself? Well, I went to my art history background for that:
The picture is by Piombo and is from the same more-or-less Late Renaissance milieu as the stories (Lama somewhat resembles Sixteenth Century Central Europe). I considered using this image for the cover of an omnibus of the four novels. I might yet.
I have done this to some extent for all my fiction, not just the Donzalo novels. I very much know what Ted's girlfriend looks like in 'Shaper.' Images exist for many of the Polynesians in the Malvern books. If they are not exactly how I envisioned the characters when I first created them, they give me a starting point for picturing them in my head.
Is this an odd way to work? I don't know, but it helps me. I am a visual person, most definitely. I do 'see' the scenes in my books as movies of a sort. That sometimes leads me to be sparse on description, forgetting that others don't see the settings as do I! A fair amount of my rewriting involves adding that in, to support the dialogue (though I've gotten better at doing that as I go along).
So I shall certainly keep doing it, just as I must draw maps and sketch pictures of castles and so on. I see what I write and I write what I see.