"the real error in your argument is that you seem to derive a normative prescription out of a non-normative description. That is to say, even if God made man in His image, why should this support your position?"
I'll recapitulate, then. I made 2

:
1. There is a hierarchy among species, or at least between humans and non-humans, and humans have superior authority and rights as compared to other animals. This is where Genesis 1.26 comes in: "Then God said, 'Let Us make man in Our image, according to Our likeness; and let them rule over the birds of the sky and over the cattle and over all the earth, and over every creeping thing that creeps on the earth.'" As I said, I think the privileged status of humans comes through pretty clearly here and the 3rd-person imperative in "let them rule over" suggests there some prescription rather than just description going on here.
2. Mere membership in the human race is sufficient to grant all humans the right to life, subject to due process of law and the possibility of forfeiture due to illicit behavior. The the reason given for this sufficiency is given in Genesis 9.6: "Whoever sheds man's blood, by man his blood shall be shed, for in the image of God He made man." This is pretty normative language. Now, you may not think it SHOULD be made as normative (because it's insubstantial or unsupported by deeper argument or whatever) and you may object to the prescription it makes (which would be an entirely consistent position for you to take), but I think you have to do some violence to the text to read "in the image of God He made man" as mere description.
"I don’t think there is a strong basis for rights outside of the justification that we do as we please, and we happen to like rights at the moment."
Okay, fair enough.
"Divine Command Theory and its cousins rely on the notion that God is good because He is good—a circular argument if I’ve ever seen one."
Well, yeah. I will gladly make and hold to this presupposition as a basic belief. I don't expect you to accept it or approve of it unless and until God Himself decides to change your mind. But I'll keep on with it myself.