How do you make a decal on a GUI text box?

Trying to make a GUI shop, with an image of my plane, on the GUI. I want to use decals out of my inventory how do I accomplish this?

To get a decal you just copy the ID of the decal and put it in. For example:

local decalid = 00000 --decal Id here.
script.Parent.Image = "http://www.roblox.com/asset/?id="..decalid

To get a decal of a model or player use this:

--decal of a player
script.Parent.Image = "http://www.roblox.com/Thumbs/Avatar.ashx?x=200&y=200&Format=Png&username=Builderman"--Replace builderman with the player.
--decal of a place
script.Parent.Image = "http://www.roblox.com/Thumbs/Asset.ashx?format=png&width=420&height=230&assetId=2153126"--Replace 2153126 with the place's ID.
--decal of a model
script.Parent.Image = "http://www.roblox.com/Thumbs/Asset.ashx?format=png&width=420&height=230&assetId=21453439"--Replace 214534398 with the model's ID.

Hope this helps!

Decals can only be on ImageLabels or ImageButtons. Not on text buttons.