Really Nice wallpaper, only thing i can see that it's missing, is like u mentioned "more realism" there could be a windmill in there i can definately picture that in this piece. The grassy part looks good, but still the division is too visible, were u trying to make the appearance of it having depth as it got further back? if so, would help to make the grass closer to the front be lighter and darker further back. The sky is beautiful, grats on that, last but not least the filter u used on the image as a whole, it doesnt help it much, just adds a feel that its missing things. But yes...a good piece indeed :)
(forgot to add this: The title, would look better near the center right, instead of lower right, just use a nice filter to make it stand out (sky light blue gentle glow maybe?))