Also, if it worked please consider upvoting this thread and leaving a comment that it worked, if it didnt work please add me ingame (Shunpaw) or in skype (power_of_ensaras) I'll make sure to help you personally
First of all, download SIU (SkinInstallerUltimate)
NOTE! YOU CANT DOWNLOAD IT WITH FIREFOX (dont ask me why :_ Just use another browser, e.g chrome!

Then put it in a folder named SkinInstallerUltimate and unzip it.
Now there should be a "Skin Installer Ultimate" exe in the folder.
Start it, then let it load to 100%.
After that, click options -> Edit All Preferences -> Uncheck the option: Fix Skin Textures with Format DXT3
Then, download the Winter Map **UPDATED** ->

Now you have a SnowRift DaySDv3
Now, you drag that folder on the "Add to Database"
Then you just press "OK" and let it run through.
Now you tick the Skin and press "Install"
After it's done you should be able to play 5x5 games with the Winter map Skin, BUT PLEASE Try first in a custom game so you make sure to have done everything right.
__________________________________________
Original Post in Lol forum
: Shunpaw Orginal Maker:

Screenshots made by Shunpaw
Some Ingame Screenshots:
and my pic:







