Thanks guys !
The pics are a bit highlighted, on darker ones the bronzes and whites look less "flat" :
And yes, you are right for the base : I am not good with bases, and I don't know what to do : this one is based on a tutorial based on cork, drybrushing and pigment, but there's something missing on it, I will check on the dakka galery to find some inspiration. I though maybe ruins, or dead trees, if you have ideas, they are welcomed !!!