Hi Lana,
The scanner review page that Blake linked to lists all of the scanners that have been officially tested and certified by Laserfiche. However, that does not mean that those are the only supported scanners. In fact, virtually any ISIS or TWAIN scanner will work flawlessly with Laserfiche. It's just impossible for us to test and certify all the scanners out there.
If you're concerned, it is definitely possible to have specific scanners certified by us. Essentially, you'll need to send us an unopened scanner that you'd like tested, and we'll put it through the paces for a couple weeks. If it works as expected, the model will be certified. In reality though, basically any ISIS or TWAIN scanner you send us will work as expected and will be certified.
One more thing to consider: even scanners that "aren't supported by Laserfiche" can be configured to work with Laserfiche. For example, a scanner that can't interface with Quick Fields can still output images to a network folder. From there, Quick Fields can pick up and process those documents, exactly as though they were coming directly from the scanner.
Basically, you should be concerned primarily by finding a scanner that will meet your customer's needs, not a scanner that works with Laserfiche. They all work with Laserfiche 