I've just added Yafray to my bag of tricks, and rendered a couple of images.  Based on what I'm seeing, there's a LOT I don't know about Yafray!  I uploaded an image to the Blender gallery here on Renderosity yesterday of a room with a table lamp.  The image I posted was rendered in Blender internal.  When I rendered it in Yafray, this is what I got.  It's the exact same file - the only thing I changed was the Blender internal / Yafray button.

Aside from the obvious lighting differences, which are quite a bit more radical than I had expected, there is now an empty picture frame on the wall.  What happened to the image?  It's just a jpg, like all the other textures in the image.

Should I be using different lights?  Different settings?  Where do I start?

Please keep in mind that I'm an accountant, not a techie, and I'll be quite grateful if you'll start slow and use short words!

"If your pictures aren't good enough, you're not close enough."  ...  Robert Capa