First of all, I can say that a lot of the inspiration for the way many of the trump cards in the Rare Triumphs are drawn comes from early and regional Italian designs. Some of the very early examples of Italian tarots include the various individually made hand-painted and gilded Visconti type tarots. While the typical regional patterns include Bolognese, Florentine (also Minchiate), and Sicilian patterns, some of these are still produced and used for tarot games, though the patterns developed quite early and have changed relatively little over the years. So some of the cards I've drawn have very classical imagery from these traditions.
What you see if you look at a lot of these classical old tarot designs is that for most of the cards there is more than one typical way of drawing the art to represent a particular subject. So for example, depiction of strength (an allegory of strength) may be a lady with a lion (specifically a lady astride a lion's back with her hands around the lion's jaws) ... or it may be a lady with a falling pillar. Or a variety of things may be happening underneath the sun, moon, and stars. Or ... lots of the cards have this kind of variation. And a particular variation might also be seen in several places.
I have mentioned the so-called Mantegna tarot before, and you will remember some of the lower-numbered trump cards in the Rare Triumphs are inspired by the kind of states of man part of the so-called Mantegna tarot. This is a series of images made by the engraving printing method, more refined than typical woodcut cards. And a lot of the imagery seems to have been borrowed from tarot cards. So of course some of the way I drew some of the Rare Triumphs trumps was inspired by the so-called Mantegna images as well.
Mitelli's tarot has a really interesting approach. The art style is rather more sophisticated in its appearance than the simpler, more naive woodcuts typical of many old tarots. But the subjects themselves are sometimes rather stripped down or alternative representations. Some of them are drawn in an unusual or maybe even unique way. For example, the lightning card just has a man being struck by lightning; instead of a hanged man, we see a rather explicit act of betrayal illustrated on the card. In the end I didn't follow Mitelli on either of these two cards, but you may see reflections of the Mitelli tarot elsewhere in the Rare Triumphs, as well as perhaps in my overall way of thinking.
The Catelin Geofroy and Anonymous Parisian tarots are unusual, within the classic woodcut style, but rather eclectic in their illustrations, probably more so than I wanted to be, though you may see some small things in the Rare Triumphs that might be inspired by these two. Perhaps it's also interesting to think about the pip suits of these tarots. The Catelin Geofroy is very unusual in that it has suits of birds (notably it has this in common with a probable ancestor of tarot described by Marziano da Tortona; bird suits were also found in German playing cards, and I remember looking through these bird-suited cards at the time when I was making my first set of playing cards, in the style of German hunting decks, with two bird suits). The anonymous Parisian tarot has the usual tarot suits, and yet things are not quite as usual as they might seem ... the suits are not drawn in the Italian style with straight batons and curved swords (as seen in almost every old-style tarot deck, including Marseilles cards), but in a way resembling Spanish playing cards. So probably the most significant thing my cards have in common with these two classic Parisian sets of cards is that they have a less typical set of suits!
Finally I will mention the Vieville tarot and the related regional tarot tradition called Flemish or from Rouen (in unrelated old news, of course Rouen is also thought to be the source of the English playing card pattern). One of the cards in the Rare Triumphs is clearly drawn in a very characteristic way that is familiar from this family of historical tarots.
So maybe that gives a little bit more insight into my influences in drawing some of the trump cards for the Rare Triumphs. I have been quite general in what I have written here, but it might give you at least some insight into where I am coming from, and even into what sort of historical cards are out there if you want to look into it further.
You can order the Rare Triumphs tarot cards here.