I think he looks o.k. You could keep the spines white to focus on the model, keep them in a colour near the body's blue or purple, or go full contrast by painting them in the complimentary colour, so orange. I think I'd take purple and then highlight to white. Maybe glaze it with purple?
That's what my wife suggested, too. Now I am contemplating: just bone color or with brown/black tips? I tend to say just bone.
Just bone, the shield will be a focal point and the underside will help frame his head so I would go dark.
I agree with Crowsfoot. Bone spikes. I usually paint my "bone parts" with GWs Baneblade Brown, then wash it with Agrax Earthshade (letting it pool near the base), then drybrush either Ushabti Bone or Ratkin Flesh near the tip. That makes a really good gradiation of color. The Shield and Weapon will be your stand-out spots of color. If you are worried about the skin looking too dark, which it might not be - just personal preference, I'd suggest ONLY drybrushing with a white on the raised areas in a direction indicating a light source. For example, the bend in his tail, I'd drybrush the top "arc" of the tail so that it creates more of a 3D effect without lighting doing it for you. (Also, shining a single light on the model from the direction desired, will show you where your brush strokes need to flow from. I usually take a pick when I get the position just where I want it and use that for reference while handling the model during painting.)
I would pay attention drybrushing white. It can get chalky easily. I personally would keep the claws and spines bone colour, with a sepia and then agrax wash at the shaft.
That's one reason I use Ratkin Flesh for my "white" tips. It prevents that "chalky" look and still gives a sharp point to a bone tip. It's also already in the brown-bone color family.
I think @Crowsfoot already gave a solution. A glaze should work wonders. I'd tend using purple, to get a near colour as shading.
I was merely giving him an alternative solution. I DO however think that he needs some warm color variation from the cold color scheme that he currently has.
Short update: I kinda decided to leave the skin as it is, added the eyes, scars, horns, claws, tongue and teeth. I like him a bit more now, although I am not completely happy with the eye. Armor is still missing obviously. On the feet and bottom of the tail I added some sepia shade to make those areas look less clean.
Looks really good couple of things you can do with the eye, very thin line across the bottom in yellow then shade around the eyeball, agrax would work or Drakenhoff, you could add a dot of white but you need to be precise.