I prefer them spelled Valter and Oscar, and of these two Oscar is my favorite. I think Walter/Valter might get a little V/W heavy as you already have Winnifred and Virginia. I'd go with Oscar. Maybe you could use all of them - Oscar Sullivan Walter?
Let us step into the night and pursue that flighty temptress, adventure.
PNL: http://www.behindthename.com/pnl/45898
Top: Alice and Elias
Bottom: Kensi and Eje