I am trying to change the "RED" color in this expression to an embedded image with the below code but I can't for the life of me get it to show the image.
=IIF(Fields!LOTQTY.Value = Fields!SIALLOCQTY.Value, "LightGreen", "Image1")
Image should be set in BackgroundImage section not in BackgroundColor section. You can set that if your value is such to display color, display that LightGreen color, otherwise put NoColor or transparent. In BackbroundImage put expression that shows either image or nothing (depending on your value).