[Sythalin]

    frame:SetBackdrop({
        bgFile="",
        edgeFile="Interface\\Tooltips\\UI-Tooltip-Border",
        tile="true",
        tileSize= 32,
        edgeSize=10,
        insets = {left=5, right=5, top=5, bottom=5}
    })

Just change the edgeFile to whatever you want it to be at any given point.