Awesome work dude! I can see you're going for some concept-art realism and you've gone pretty far! Definitely on the right track. There could be better color choice (and you admitted this was a challenge) while for the landscape/background I think it was actually the strongest part of this piece! The foreground is done well of course, but it blends too easily to the background. Better implementation of light effects (shadows, light-scattering, highlights etc..) could really improve your piece although the yellow flower thing looks really nice! Again, great work pal!