Exterior Concept - Beginners Render

Looks like you're heading in a very positive direction. Since you've been looking at Peter Guthrie's fine site, have a look at his tutorials on Vray dirt and using the Vray edgetex map in the bump channel to soften corners. One more suggestion is to use camera correction to keep the vertical lines straight.

The only thing holding this image back is the textures as you said. The grass itself isn't that bad, it's just the color/texture, way to saturated. I like the modeling but I could probably shave with a few of those sharp corners, especially the curb :) Get some hi quality textures and this image will be top notch.