But I do know that using a picture that makes you look uninviting, or dare I say freakish in a not-on-purpose way (I've seen author pics where they've zombified themselves and those are unique and cool), is not a good way to represent yourself professionally.
You don't need to spend a lot of money on author photos, although a professional will usually get you what you want in a shorter time frame. If you put the word out that you're looking, you can often match up with a student needing to increase their portfolio, or a photographer just starting out.
My critique group found a portraitist through the local camera club and we made an afternoon of it--we had time to change outfits, get creative with lighting and a wind machine, and do a kooky group shot. And all for free.
And my latest find is an Old Tyme Photo Studio at Marshall Gold State Historic Park, where you can dress up and get your picture taken for $7. Even if these don't get used for an author photo (although, my first book is set during the Gold Rush years), they make for a memorable profile pic. That's a bargain, for $7!