@monstahunta: Did you use reference for the painting of the flower (?) or did you use reference. It looks interesting, but I'd be curious to know more about it before offering my two cents. 

I think the best advice I can give you right now is to read through [url=http://illustrationage.files.wordpress.com/2013/04/andrew-loomis-figure-drawing-for-all-its-worth.pdf]this[/url] book and do some of the exercises in it. Andrew Loomis will help you to get your anatomy/proportions correct. He's an excellent resource while you're trying to improve -- don't be afraid to tap into him! Anatomy is a difficult and frustrating subject to study, even for professionals. (Most will refer to anatomy books and/or shoot reference pictures to help them get it right when working on a piece. There's no shame in getting a bit of help, especially while learning!)

When painting, never paint on a white background (applies in both traditional or digital mediums) -- the reason for this is that it'll mess up your value scale (darks/lights) because you're constantly comparing everything to the brightest value there is. This will make work look washed out and, if working in colors, it'll make things look very dull/lackluster. Always tone your canvas. Pick a medium tone (it can be any color you want because you're just going to paint over it all anyway) and fill the entire canvas. Once that's done, [i]then[/i] start your painting. It'll improve your contrasts/values and color work tenfold.

@Roran: Don't paint with white! (See above comments.) 

Get reference for that armor and do a study. Try to see how the light works on the surface of the metal and understand why. Which direction is the light coming from? Which highlights are reflected light from the environment the armor is in? How do the shadows work and what colors are they? Metal can be tricky to render and definitely requires doing actual studies to get it right.

The Shinobi pieces aren't bad. Nice foreshortening for the pose. You seem to have a tendency to make your heads a bit on the too small side for your figures. I'd recommend checking out the Loomis book I linked monstahunta to above -- it should help you straighten the issue out. 

I particularly like the profiles on the 'Lords of War' pieces. Good proportions and nice expressions. (Each face definitely has a bit of personality to it.) Profiles can be hard to do sometimes, so kudos on those!

@Brand: Since you have a bit more experience, I'd recommend doing some studies from [url=http://www.scott-eaton.com/outgoing/books/George-Bridgman-Constructive-Anatomy.pdf]George Bridgman[/url]. It looks like you're guessing a lot on the actual underlaying structure of your faces/anatomy and I think you'd really benefit from doing some dedicated construction studies. Bridgman is great when you already have a bit of knowledge under your belt -- his constructive methods are top notch. (And his line work is really excellent, too. One of my favorites.)

The 'random' piece has a nice color scheme, but you're right about the head not interacting too much with the environment. It almost reminds me of an attempt at 'shape sifting', which is a style of art that [url=https://www.google.com/search?q=Android+Jones&safe=off&biw=1365&bih=832&source=lnms&tbm=isch&sa=X&ei=EyYTVPq8N_easQSIwICACQ&ved=0CAYQ_AUoAQ]Android Jones[/url] came up with. His work is really interesting to look at (another one of my favorites) -- every piece is built from using miscellaneous shapes to paint with, repurposing them into other items as he goes. It's really cool to watch him work.

[url=https://www.youtube.com/watch?v=sKgRZEYA8tg]Some[/url]
[url=https://www.youtube.com/watch?v=7yP723_EcKc]videos[/url] 
[url=https://www.youtube.com/watch?v=Xyx6odbrGsE]of him working[/url] 
on a piece that's kind of similar to the to the idea of the two pieces you did.

Android does a lot of live shows now where he'll go to a club, then a DJ will play their set, and he paints live on a huge screen while people dance/party around them. If you look him up on youtube you can find a lot of his performance art and it's cool to watch him work and see what the music is inspiring him to create at the same time.

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Keep up the good work, guys! 
(Sorry again for the delay! My new floor literally just got finished being installed about twenty minutes ago. It's been a bit crazy around here. lol)