Let's make a character for this artwork

[jaappleton]

(If you know what the artwork is from, please, please disregard that knowledge. I'm not trying to recreate the actual character in D&D terms, but how you'd stat up the character based strictly on the artwork)

So, here's the art itself:

http://orig10.deviantart.net/ff02/f/2017/108/4/8/cosmic_blade_master_yi_render_by_zactheacorn-db6ap0x.png

Now, at first glance, you may think "Whoa, that isn't medieval fantasy, that's more space related". And I certainly see that. But let's play, shall we?

To me?

Warforged
Warlock: Seeker Patron
Pact of the Blade

This is a Warforged created by the some sort of Cosmic force. I'd go with a Star Pact if 5E had one. I think the Seeker is as close as possible, though I could see Undying Light or Celestial working as well.

Now, playground, I ask you:

What do you see there?

[Crgaston]

High or Dark Elf... Ancients Paladin/GOO Warlock, Tome Pact. Disguise or Alter Self invocation for the groovy face/costume.

Sage Background... The character's curiosity in studying the Old Ways led to delving into numerous ancient manuscripts, until poof! Ultimate knowledge.

[Sirithhyando]

First thing that came to mind is the Aetherborn from the "Planeshift : Kaladesh" and same as you for the class, seeker warlock with blade pact.

edit : out of curiosity, where does the artwork come from?

[jaappleton]

First thing that came to mind is the Aetherborn from the "Planeshift : Kaladesh" and same as you for the class, seeker warlock with blade pact.

edit : out of curiosity, where does the artwork come from?

I hadn't even considered Aetherborn myself, but it fits quite nicely! Well done!

The artwork in question is actually where I get a ton of my character inspiration from: League of Legends. I've never played the game myself, but all their heroes have tons of 'skins', so there's tons of versions of each character. This one in particular is the Cosmic skin for Blade Master Yi.

[lunaticfringe]

Half Elf Noble Eldritch Knight. It's scandalous for a proper lady to adventure and engage in fisticuffs so she dons a set of custom Glamoured Armore to hide her true identity.

Sailor Batmoon.

[Dudu]

Didn't like that artwork, just not my cup of tea. Too flashy, with actual stars and stuff.

But I would go with OP's suggestion, a warforged. And Bladesinger looks like it's class (subclass).
Of course, bladesingers are elves by default, but even the book itself says you can easily handwave that requirement without the slightest impact in balance, so a warforged bladesinger it is.

Valor bard could work as well.

[wilhelmdubdub]

An Aasimar horizon walker would work too

[Finger6842]

A male drow fighter wizard delving the astral plane in search of a gift for the goddess lloth.

[Mortis_Elrod]

Owning this skin its kind of hard to disregard the knowledge of the character but i'll try.

Seeker Warlock Maybe Drow,Aetherborn,Eladrin, Aasimar.

Eldritch knight/bladesinger

Celestial (meaning heavenly, but pertaining to the cosmos and other 'celestial bodies') Warlock. Blade Pact

Really like the Horizon Walker idea, would multiclass that with Seeker Blade Pact for extra flavorful person.

All of these are pretty good for the artwork and not far off for the character.

I also get alot of character ideas for League of Legends, though i play it so its not just the skins giving me ideas. Would love to do this with more skins and different artwork. Sounds like fun theory crafting.