Sorry for the late answer :s.
First, thank you guys for your opinions ^^). Well, I think @KrzysztofZwolinski was right, I agree with the fact the neck determine the spine, so I'll choose the slope one.
So do you think that the back legs are too skinny for the slope one @nomadking ? Should I thicken the shin of the creature to make them look more strong ?
Else the workflow of the texturing is simple.
I've worked with symmetry, I've imported the UV Map in Inkscape in order to draw the pattern of the creature's back :
Then I've generate the AO map that I've combine with the pattern and the colors that simply paint with Gimp. The AO Map is in multiply mode on the colors.