Few things I want to say up front – if you make business cards for your author-face, please have these pieces of information on it: your name, email, and website. I would caution you against normal business card stuff like phone and address because you would not want to hand these out to casual readers or fans. You’re not advertising yourself, you’re advertising your book.
If you want to put your genre – go for it.
If you want to put the name of your series – go for it.
If you want to put a quote from your book or your favorite review so far, as quoted by some famous uppity-up author – then all mighty heck – go for it!
But please take into consideration who is looking at these business cards and why you’re printing them.
A lot of business cards are rather plain, with only a small logo from the business in the corner, but since you’re an author/writer, then you can have as much freedom as you want with these. I would recommend your cover, or another thought-provoking image for the back. Here’s a sample good design:
Maybe here you can include a few slices of covers from a book series, or character head-shots/drawings. I like using pictures more than words because a picture is worth more than a thousand words, etc. They sit better in my mind than a specific quote, which I’m less likely to recall. It’s easier to remember an image than it is a sentence.
If you can convince your cover artist to do a small design for business cards, maybe that might be a good idea. That way it doesn’t look the exact same as your book cover, but it still holds the same theme.
Your face could work – and I’m sorry how superficial it sounds – but you should have a nice set of photographs and be slightly photogenic. I would recommend to have professional photos taken. Plain backdrop, nice outfit, etc.
If you can’t have an image, aim for something simple. Print a word or short phrase from your writing. Like a code-word from your books, your genre, a simple phrase like the one shown below.
These are only a few ideas. If you don’t have any designs in mind and/or can’t make one yourself, I would recommend to travel to Moo and see what they already have. They have a huge list of pre-made designs, and this is their line of work. They’re good at what they do. I’ve used them a few times already.