I think the only strong argument for God's attributes is philosophical; that since we are free-will conscious creatures; in creating us, God would have to have at least these same attributes.I just wouldn't know what to base that belief on. I could imagine any God I wanted. However I wouldn't really assume any reality to that imagining since it would just be a product of my mind.
The same for God's existence. It is hard to imagine how this universe with all its intricacies could exist without some purposeful conscious mind capable of creating it.