Critique time!

Hi, great work so far
I like your design and your rendering on the hover bike

I think you could improve a bit on your values. The background and the foreground look both a bit gray. A good idea is to have a muted Background and higher contrast with your character so it pops out and separates from the background. The Levels in your painting look like this:

The gabs mean lower contrast. But for your Character you want something like this:

so you have a higher contrast. (In Photoshob you can open the Level adjustment with Ctrl+L)

another thing i noticed is that you skin looks a bit strange because you only change the values in the darks and not the color. Here is a tutorial on how to paint skin

I did a quick paintover to show you the difference of these two things I talked about.
I hope this was helpful

ps: \m/

Alright so right off the bat I see a lot of things in which you can improve in, and let me tell you that's an absolutely amazing thing. Many times artist struggle on what they can improve next, or what there pieces are missing so rejoice! Alright so lets dig right in shall we?

Your Anatomy
There are many parts in this piece where the anatomy just to put plain simply... needs work. Luckily for you there are tons and tons of free courses on youtube in which I recommend Sycra Yasin's how to draw and anatomy series. No matter how experienced we believe our selfs to be there shall always be more to be learned.

(you may already know of sycra, your style almost reminds me a lot of his now that I look at it)

Lighting
- The lighting has a huge affect upon how we perceive your character, shading you character in black usually doesn't bode to well with your characters image as it gives them a dead, pale type aura, however there are times where it can be used to your advantage! Sycra also has an AMAZING series on the fundamentals of light and shadow I'd definitely check it out. What I feel your missing is the base understanding of how light works on objects of different texture and material.

(the person above just posted a skin tutorial right as I was typing this, cool.)

. Composition
- This is where in your case you want your character to be the focal point of your piece. There's just one problem with that, the saturation of colors you used in the piece stays the same through out the entire piece, so it's almost as if she's blending in. Again this could be advantageous at times , but for know I'd say it'd be a great idea to vary your color palate.

(The machine in the back-round remind me of the ghost from halo, I really liked the sharp edges on it by the way nice execution.)

Over all I liked the piece, and If I could give you one word of advice, just have fun and (BELIEVE in the PROCESS) because theres no such thing as failure, only feed back...

Cheers! -Exofley signing out.