[StreamTexture:1458] cannot be used to get your texture, it is only a debug representation made by the
str() functions. If you got it from a file, this won't work either.
To obtain the texture you have to know its path:
var TextureReference = load("res://path/to/texture.png")
Or you may want to assign it from the inspector in the editor, by using
export(Texture) var TextureReference