Without even changing any color, I would advise your to paint deeper highlights to help the mini to stand out and improve mini "readability". Trust me, that would change the overall result a lot.
Regarding the color, this is more a matter or personal taste. The colors you've chosen and the way they are kind of mono-chrome are interesting because they are grey and dull, creating an "out of the tomb" atmosphere. Still, mono-chrome are somewhat more appropriate for 28mm...
If you want to change the bones color, you can paint the skels brown, brush them bone-white and lightly brush them pure-white. On the giant you will have to use highlights instead of brush if you want a perfect finish; and the add a bone-weathering effect you could wash it irregularly with a 80-20 mix of water-chestnut ink.