For starters, I want to thank you for having me critique one of your works. Truth be told I didn't intend on having the longest critique to be TL;DR for you, and have your eyes grimace because of the long paragraphs, but apologetically I wish for forgiveness; this picture is one of my favourites and Miku is one of the few characters that, in art, you can really express in your mood tying to hers; whether in it be sadness, happiness, or whatever. But that's beside the point. Let me begin on the critique.
Vision Appearance-wise, this picture is captivating. The background and amount of effects featured in the picture is astonishing. It really adds to the image of APPEND via Miku, in my opinion. Whether she is in the ocean, air, or in some type of cyber-like environment, it truthfully adds to the overall scenery.
I, however, wish that Miku's expression herself was a bit more joyous, or, if you were going for the more saddend or mature-type look, arched her eyebrows ever-so-slightly and less confusing. Preferably I would lose the microphone and featured just Miku and her assistant fish friends; the microphone seems to be out of place.
Originality This category, in short, is extremely debatable. The character can be argued for originality, howevr the picure itself seems to be a bit more original than most APPEND arts I've seen. Many reolve aroun more digital-type themes and after awhile, it becomes a bit bland, but yours seems to have a bit of creativity behind it. In particular, the fish that are surrounding Hatsune to a distance reprsent more than simply aquatic animals, but the assistant scenery and theme of anew.
The background and effects, as previously mentioned, are extremely wonderful and perform an excellent amount of adoratin towars he picture. The shades of blue really add to Miku's image and make the image all the more exquisite. I'd just be a bit weary of the amoun of effects; don't make it look too PhotoShop-y.
Technique I love your style of imagery. It seems that there are only a few set of colours that you actually use, and while mixing the d ifferent shades add all to the overall blue shade, makes the portrait beautiful.
Generally with VOCALOID themes would be plastered moreso around music and simply again, digital scenery, but yours seemed like a more carefree, almost ocean-type of view. I really like it, it differs in a good way to a lot of other arts. The background at first seems to be a bit plain, but slowly evolves into a more complicated and more sophisticated image.
Impact Overall, I could say that the impact was great and nonetheless, bring a more sempiternal memo. It completely dazed with the amount of backdrop it had; theme, colours, just everything. Moreso this is bewildering. I c an't possibly continue with compliments on the picture altogether.