I think you're being too hard on yourself Diolma! I learn more from my mistakes and failures(had plenty of 'em,lol) than I do from my effortless triumphs. I would suggest bringing the shoes and socks closer to the camera. If you give the shoes a lighter color, even if it's a lighter brown, it will give more contrast and draw the eye as a focal point.

Since your terrains are close to the camera might I recommend some tiling photographic textures? The site that Rochr recommended a couple of days back has some great non-copyright textures, including several kinds of sand. There are several good tutorials on making waves here in the archives and elsewhere.

All I'm saying is, give yourself a break and don't get too frustrated. Most of the artists here whose work you may admire had to go through all the steps of learning that you're going through. I think this has the potential to be a great scene, and I love your theme, so don't give up. End of speech,lol. Dan