Izzy,
Sounds like you're already planning your clothing well. But, make sure you wear layers that can be taken off or put on easily. It can be substantially below zero in the morning and you'll be sweating by noon chasing those hounds. Then, by the time you have that cat skinned and in the bag it will be very cold again. I like wool. You don't need camo, but a nice plaid shirt or a camo jacket will look nice in the pictures. Also, most outfitters have a small tape measure, but bring one just in case. Make sure to ask the taxidermist what measurements he will want. You want to make sure he makes the form fit the lion and not the lion fit the form. In otherwords, you want to make sure your trophy comes out the right size. Make sure if you take pictures in the snow to move your lion to an area with fresh untracked and unbloody snow. Then the pix you post here will look great. Finally, make sure you stay hydrated. Drink plenty of water before, during and after the hunt. Even in cold weather, you will dry out fast and the water will help combat any altitude related problems you may encounter. Have fun!
Mike