As a digital work and customization I can't find anything particulary wrong or out of place, however within the purpose and direction of a wallpaper it seems a bit off or out of place.

Not that the direction you took is particularly wrong but one suggestion i have is on the background. True she feels but within a dream but the surrounding sandy color sorta imbalances that a bit. A suggestion would be to make one side a more solid color such as white, (left) so that it flowed from the left and into the right side. Her gaze and softness are lovely but if you spread the white over her shoulders or at least left the impression they were there it would bring a closer feel to her emerging as an apparition of some sort.
Those are just little suggestions overall you truly accomplished a beautiful wallpaper. ^^

You want someone to critique this? That must imply that you see something wrong with this. If there is anything amiss, it is surely to your eyes alone, for I can find nothing. I'm even actively searching for fault, and I can find nothing. I'm so dazzled by its beauty, that I'm not entirely certain I am capable of finding fault, even should I look for hours.

I love how the viewers eyes fall directly upon the green eyes of the figure, even though the figure is gazing elsewhere. I also love the fullness and softness of the lips. Forgive me for saying so, but those lips seem very kissable, which is something that can only be achieved through great skill. Noses are my bane, but you have mastered the craft. My great hope is that I may be as good at drawing faces some day. Though I must say that what really dazzles me is the sheer brilliance of LIGHT in this image! It's the sort of light that chases away shadows and leaves no room for darkness. This is a being of supreme good, perhaps even a deity. I love how the light radiates from her hair giving the impression of a halo without drawing upon that cliche.

This work of art is inspiring. The figure strongly reminds me of one of my original characters. It makes me want to drop all of my obligations for the evening and set to work writing about her instead. You are a muse. I am truly awe inspired.

I'm sorry. That really wasn't much of a critique. I have said nothing that will help you improve as an artist. I hope that you find this comment useful all the same.