Hi Lost Girl,
I've been working on a tarot deck for about 8 years now and here is my advice, use whatever is good to you and dump the rest! My advice that is
Over 78 cards you will learn a lot about tarot and I don't think there is a way to make a perfect card ever because you are always changing and growing and the way you view tarot will change and grow too. Each card is a snapshot in time really. I would just do the best you can do at that time and if later you decide it sucks you can redo it.
Take into consideration your motivations for making a tarot deck. If it is to be a personal art peice totally feel free to use different fonts and borders or styles or whatever! Who cares!
If your motivation is to learn more about tarot you may want to learn about some of the older decks which were innovative and inspirational, and learn how and why they used the images they used. These decks could be the Thoth, the Rider Waite, the Tarot of Marseille, the Visconti. You could get 78 degrees of Wisdom by Rachel Pollack (which I hear is having a problem with distribution presently) or Mary Greer's Tarot for your Self.
If you want something that is commercially viable, I would still personally suggest doing it from the heart as far as borders and fonts go, I mean, do what you like and what you know and make it the best you can but to make things easier you might want to keep all the images the same size and have some consistency and also try to understand the reasons behind the symbols before departing from them. A lot of that stuff isn't arbitrary and people like those powerful symbols included. I know some deck publishers prefer to publish decks which are based on the Rider Waite pattern, for example. They also want to see people on all the cards, and illustrated minors, not just the suit symbols.
A lot of people like traditional titles and suit names and numbering. A lot of people don't like card backs that you can't reverse. I think borders, while fun to create from the design point of view, are accepted or only tolerated by a lot of people, they want to see the art.
There are exceptions to every rule! Do your best, learn as much as you can and just make art and you will be ok. You will always have time to go back and revise but I don't think there are any mistakes here, even cards which are eventually rejected will teach you something.
I know there are websites which list some of the major symbols from each card, if I find them I will post them (my computer crashed recently and I lost all my links) Michele Jackson used to have one and maybe Bob O'Niel does too. Oh, Arnell Ando might! I'll try to look up that stuff later and post it!
Good luck and Welcome!!!