Good basing is important to the look of an epic model as the base to model ratio is much higher than with 30mm. None of the three you have done is jumping out at me as looking right with the model somehow. I have a few alternative suggestions you might like to consider:
Graveyard Earth; it's my favoured choice for earth bases, particularly for dark coloured models where you need something to lighten up the overall look. It's gives a very neutral, natural, earthy look. I did my Raven Guard with a heavy drybrush of Graveyard Earth over black and then a very light drybrush of bleached bone on top.

Or possibly a light sandy desert base? I did this with desert yellow, heavy drybrushed with Rotting Flesh and the Rotting Flesh with a little white in.

Or a really left-field suggestion but possibly Martian style reddy-orangey dust could contrast well with the green? (though I may have gone a little OTT in the orange-ness on this one), this was made of a mix of 3 Mig rust weathering powders.
