While I can see that the different colors on the linework are just to help you when making the final linework, I really think they add a nice touch to the drawing. The contrast between the red skull and the blue beard on the right is fantastic, It really makes a simple oldschool skull tattoo feel so much more alive. I'm really curious to see if you'll be able to add this same feel to the tattoo itself, maybe with softer lines and coloring. I think both skulls are great, the right one looks more finished, but I can see the same potential in the left one.
looks great so far... are you going for colors or black and gray? either way I am sure will draw it well.. my humble opinion is that you can play a bit with the queen's crown.. I would have tried to make it look more expensive and authoritative. That creates the contrast of the dead human which was probably rich and powerful while she was still living but in the end material wealth can do nothing against time, which eventually recycles everything.