First off, this is indeed a lovely shot as a whole. The scene is wonderful and unique... I've seen creeks and pools, rain, forests, all sorts of urban settings indoor and out, and even fountains, but they were small. This is, what, a very large fountain? As I said, unique... which is good when trying to portray a character who's so vain and craves uniqueness (though it seems to have been born from craving conformity).
The costume is well done and needs to be in order to pull off the image. It lacks some of the finer detail (bracers, arm band, coat edging) but appears to be very well tailored by someone who is fairly good at the sewing machine. I would suggest perhaps materials that are less shiny except for where Loki's costume is actually shiny. Also, a stricter color match-up would make the ensemble that much more appealing. HOWEVER, do not let that make it sound as though I am not in awe of the work that HAS been put in. It's obviously been well thought, drafted, well shopped for and executed.
The actor in this work is deliciously asexual and while I know that she's a she (due to seeing her work before), she can very easily pass as a man and does it very well here. Passing as a male is NOT (obviously) an insult -- necessary to make clear due to having heard, in my lifetime, otherwise. In truth, being a woman posing as a man with such fine facial features works very well in the actors favor here. Some shading on the cheekbones (or more if it's already been applied) and bridge of the nose would create a sharpness to better match up with the Mr. Hiddleston.
The actor's hair is styled beautifully! There is a very specific length as well as color, hairline and feathering is necessary to ensure the hair looks proper rather than appearing "off". I have seen many Marvel movie Loki costumes where the hair, unfortunately, detracts a bit more than it should from the overall experience. Either the wig makes a harsh line across the brow or the color is more of a blue-black rather than true-black or the cut is wrong... In this image I see that the hair has been feathered to stand away from the back of the head rather than just plastered down and there is no unsightly over-curling.
Expression-wise this is done very well. The pose of the body, arms folded; the tilt of the head, not facing straight on... refreshing. I enjoy the lack of a weapon as it is usually heavily prominent in most Loki cosplay pictures; usually being wielded in a threatening manner. The expression here is not glaring, not manic, slightly peering out from underneath the eyebrows, lips not pursed, not cocky but there seems a smirk about to happen. This person has good facial muscle control and knows what they want to show in their features. Bravo!
Aside from those minor points I mentioned about the costume itself, which can and is completely excused due to it being so well done to begin with and very easily identified, I take slight issue with the amount of skin showing. Let me explain: I don't believe that Loki himself would be opposed to getting his shoes or pants wet. I truly think that the best way to improve on this scene would be to be fully costumed and allowing those parts of the costume that would be, submerged. If the actor here does not want to "ruin" their shoes, then purchase some cheep boots and do up the tops to appear like the final perfect version. Also, create another pair of pants and allow them to become wet... launder them or make more; it would be for the best in a shot as serious as this one.
P.S. What is that smudge at the lower left of the image? A thumb? A trick of light? It's... detracting.
Why is everyone set on the "duckface" expression, I don't see a duckface...I see a proud little smirk...but no duckface. More of a snooty I'm better then the world, expression, which is very befitting. I love the cosplay, the model, location, everything. Looks very believable and one of the best Loki look-a-likes I've seen thus far. Wonderful job on this!!