Do you offer custom collars?

Yes, I can do any solid color for the same price :D

I wanted to inquire about a collar similar to the one shown in this piece --> http://www.furaffinity.net/view/13232421/
Would you accept a commission like this at this time?
If so, how much would you charge for something like that?

At this time I am not prepared to do anything including spikes, I've done a few spiked pieces in the past to varying degrees of success, I need to figure out a better way to approach them before I can take a spike collar commission again, sorry to dissappoint.. However, I can do a solid-colored one that matches that color, sewn in a similar fashion to the ones displayed on my etsy store. That would be $40 + shipping.

Do you think it would be possible for me to add the spikes after, if I purchase the collar? Or do you think it would too difficult?

Depends on how you want the spikes to look of course! But if you picked up some screw-in metal ones that match your character's look and the scale of the collar I don't see why you wouldn't be able to just punch the holes and install once you found the right ones.
example:
http://www.turnbolt.co.za/assets/images/SPIKE.JPG
https://img0.etsystatic.com/012/0/6.....66806_5403.jpg
http://www.mjtrim.com/media/catalog...../37159-s_1.jpg

I haven't ever found any in white (they tend to just be in chrome) or at a scale that matches fursuits, but I certainly don't see why you couldn't install them afterwards. I hope that gives you ideas! :D

The color of the spikes are suppose to be a gray color anyway. Sorry the ref is a little off.
Thanks for the information! I think I may wait until you open up for spiked collars. :)

Ohh neat I like the rainbow one!

The rainbow one is the most fabulous.

I totally got one ahh <3

Is the color of the 2" green collar more accurate in the first 2 pics or the last one? In the last pic it looks kinda blue-y. :3

Honestly its the same color just photographed on different devices. Also it seems to display different on different monitors as well.