WoW:API Frame SetBackdrop
Syntax
Frame:SetBackdrop({bgFile = "bgFile", edgeFile = "edgeFile", tile = false, tileSize = 0, edgeSize = 32, insets = { left = 0, right = 0, top = 0, bottom = 0 }});
Using 'nil' as the only parameter will remove the backdrop on the indicated frame.
Example
MinimapCluster:SetBackdrop({bgFile = "Interface/Tooltips/UI-Tooltip-Background", edgeFile = "Interface/Tooltips/UI-Tooltip-Border", tile = true, tileSize = 32, edgeSize = 32, insets = { left = 0, right = 0, top = 0, bottom = 0 }});