I know most likely Viking era Saxon's didn't fight on horseback, but for the Saga game, I can mount some of my Hearthguard. At Historicon I picked up a box of Conquest's Norman Knights. They come with both a kite shield and a round shield, so they can proxy in for mounted Saxon's. In between flocking the Marengo battlefield, I've manged to get a few figures painted. Mainly while waiting for things to dry.
Here is my first 4 mounted Hearthguard. This should give my Viking opponent some trouble. Dang it, I should have painted up a mounted Warlord as well.
Just checking the Saga Northern Fury rules and I can mount ALL my Hearthguard! More to come!