My script is supposed to set a value to an image url?

local event = game.ReplicatedStorage.Events.Tattoo

function leftClick(mouse)
event:FireServer()
script.Parent.Parent.WhichTattoo.Value = script.Parent.Image
end
script.Parent.MouseButton1Click:connect(leftClick)

so basically when you left click the button it fires an event (not important to my question) & sets a value to an images url (line 5), when i play and click the button, the value stays blank, does anyone know why?