Hmm... I don't think there's a should at all. Although I'd tend to have all the feet point out as well. So it'll look like doggies running in a circle around the quilt.
Or if you decide to define a top and bottom (by having the "top dogs" with feet pointing inwards), perhaps considere putting one doggie in a corner of the centre somewhere, to help define the direction?
Just saying to confuse you further, erm I mean... so you know you can't go wrong whichever way you choose! :D