Blitzer, I'm beginning to feel your pain.
I've searched the web until my eye's have crossed, and as yet I have not been able to find a picture of a Sherman, M36, or M10 in winter garb. I even looked under "The Battle of the Bulge" and didn't find anything.
I'll still look, but I'm not having a lot of luck yet.
They will look similar to German Winter Schemes except the Allies had plenty of Whitewash and as a result had more vehicles which were entirely covered.
Keep one thing in mind though, at the beginning of the Battle of the Bulge, the Allied vehicles were still in OD, they had not received any whitwash yet. It's just a thought.