[JonnyRotten]

Have you checked the strut mount under your trunk liner?

If you mean checked to make sure it's tight, yes I have.

 

[JonnyRotten]

When does it seem to happen? Do you notice it more when you're going over bumps, around left turns, etc. ? Have you checked the rubber seating on the spring? For some reason people used to install those upside-down and it would make weird sounds for them.

Here's a pic of what I'm talking about. Disregard my busted/leaking strut. I no longer have those coils on my car.
Also notice how it's not seated properly at the bottom, though the orientation of everything is correct.

That's a good idea @teamrubixcube
Yes, the popping noise happens when you go over bumps, usually at lower speeds and it's more noticeable when you are going over uneven surfaces and the rear suspension is being flexed on one side more than the other.
I did notice when I was installing the rear springs, that the stock springs are coiled in opposing directions while the new springs are coiled in the same direction so the bottom of the spring doesn't sit quite properly in the rubber mount at the bottom on the one side. (I can't remember which side didn't fit properly)
I was wondering if you bought two of the same side (two lefts or two rights) of the bottom rubber perches to match the spring rotation, if it would fit on the bottom arm properly. There are little nibs that fit into holes to keep them in place if my memory serves me correctly. You can see that in your picture. The one is not sitting in the hole that it should go in.

 

[JonnyRotten]

do you have rear camber arms?

Yes, I have Skunk2 arms

 

[JonnyRotten]

It seems odd to me that the new springs are not wound in the same direction as the stock springs are. Is this common?

I'm pretty sure it's for cost saving.
I think most aftermarket springs come with both springs wound in the same direction. I'm not 100% sure though.

 

[JonnyRotten]

I'd be willing to bet it's the camber arms. I just installed some Godspeed camber arms and I'm getting a slight clunking sound when going over uneven surfaces like driveways.

I guess it's always possible but I don't know how a camber arm would make this type of sound. All they really do is pivot. I've also made sure they are bolted on tight.