Problem is there is not one with out the leaves.
Snow on an oak would mean the leaves have dropped already.
The one in Mega pack 03 under foliage might work with some re texturing. It is a multi textured model. One for bark and one for the leaves.
EDIT:
OakTreeWinter Attatched below. Mesh is from stock oak tree from Mega Pack 03/foliage folder
Re textured and combined the textures. Re UV mapped this to be a single texture object now.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.
