Windy dog walk

I think that it is ok as it is as the foreground has enough detail in the grasses and definitely look as if they are blowing in the wind,:)

I like it, but picking up on your own point, the middle ground lies there like something of a slab - it could do with some colour variation, maybe a cloud shadow, maybe a shaft of light, and a diagonal to relieve any suggestion of a stage-set look (you know, one thing cut out and placed before another). It's a matter of taste, or opinion, but I'd also just like a few sharper, more accurate grasses, seed-heads, leaves in the foreground, shown catching the wind. When you get your oil paints, these are points you'll need to consider because to really exploit the richness of the medium you need plenty of defined marks close-to: or you can end up with a bit of a formless mass.