How to- Change mouse icon Size?

I already have a decal to put in my tool, but I don't know how to change it's size. Currently it take a very large chunk of the screen away when equipped. I have not reached far enough in scripting to know how, or if it's possible. So please, give a good explanation on why that works?

tool = script.Parent
playerMouse = game.Players.LocalPlayer:GetMouse()

tool.Equipped:connect(function(eventMouse)
    eventMouse.Icon = "http://www.roblox.com/asset/?id=111275729"

end)

It's a local script too.