Examples:

local backdrop = {
  -- path to the background texture
  bgFile = "Interface\\DialogFrame\\UI-DialogBox-Gold-Background",  
  -- path to the border texture
  edgeFile = "Interface\\DialogFrame\\UI-DialogBox-Gold-Border",
  -- true to repeat the background texture to fill the frame, false to scale it
  tile = true,
  -- size (width or height) of the square repeating background tiles (in pixels)
  tileSize = 32,
  -- thickness of edge segments and square size of edge corners (in pixels)
  edgeSize = 32,
  -- distance from the edges of the frame to those of the background texture (in pixels)
  insets = {
    left = 11,
    right = 12,
    top = 12,
    bottom = 11
  }
}

-- replaces the game menu's backdrop with the gold backdrop 
-- used in Bind-On-Pickup loot roll frames
GameMenuFrame:SetBackdrop(backdrop)