There was a thread a little while back called "Help! Summer + O type = no ice cream/fun"
and google pulls up a heap of recipes, just filter search with no dairy or dairy free icecream recipe, also sorbet, granita, etc. Just check ingredients and substitute for blood type.
Presume you're ok with yoghurt? - just add blended fruit & a little sweetener/carob/nuts(macadamia, walnut, peanut for A's etc) and shove it all in the icecream machine.
There might be something on this site's recipe section too.
My fave is the lemon sorbet on the above thread. It's winter here in Oz so won't be making any for a few months!