DImage Error/Images not Loading

[carry4]

Problem:
When ever I try to do a DImage, it's just an error(the purple and black)

How you can help:
Tell me how to link the image, (path) It's in a gamemode so what path would I need.

Current Code:
local usapanel = vgui.Create("DFrame")
usapanel:SetSize(490,500)
usapanel:SetPos(ScrW()/2, ScrH()/2/2)
//usapanel:Center()
usapanel:SetVisible(true)
usapanel.Paint = function(s, w, h)
draw.RoundedBox(10,0,0,w,h,Color(0,0,0,255))
draw.RoundedBox(10,2,2,w-4,h-4,Color(169,169,169,255))
//draw.SimpleText("USA","faction",490/2-50,5,Color(0,0,255,255))
end
usapanel:MakePopup()
local usaimage = vgui.Create("DImage", usapanel)
usaimage:SetSize(490,500)
usaimage:SetImage("Darkrp/content/usa.png")