On your Eldar, I think you've got a very nice bone/white/cream colour going. However, I'd like to see more contrast, maybe a red or a green in there. The brown/yellow is too similar and it looks a bit plain. I'd like to see more of the red you have on the hair and such on the weapons, perhaps with a little black?
I disagree with this. At the moment you have a very nice, subtle finish. I think that too often we throw colour at a mini, but in this case the muted palette works very well. Excellent paint job on both WHFB and 40k minis so far, I look forward to seeing more of your work!
As for the Greatsword base, simply doing the rolling fields of the Empire might work nicely, nice greens from static grass would enliven the model quite a bit.
If I'm honest, I actually think what makes the Eldar look drab in the eyes of DarkstormUlthwe might be the base, as it's a lot of brown down there. As this matches the brown on the minis, it does give a very 'brown' theme. Either cityfight type bases, or even lush maiden world type greens would do enough to contrast a bit with your Eldar and give definition and separation from the mini.