Oddly enough you're lighting is fantastic, and so is your colour choice - so I have nothing to say there, and I would only be patronising to comment on it!
However you have stumbled slightly on anatomy: I think you could really benefit from drawing some still-life works first, nothing too detailed - just practice sketches etc. What I mean by this is that some of your drawings are painted to good effect, and look realistic but then the positioning of your subjects distorts the realism.
Obviously, pokemon aren't real. But in order to decieve the eye into recognising the form of a creature, it has to conform to patterns that the eye would expect to see - i.e. it has to look natural.
I'll use your latest painting - Thundurus - as an example. I appreciate that you've tried to create good perspective in the picture, and it has nearly, nearly
worked. But there are some oddities which throw me; firstly, look at the shape of the torso, the right side is perfectly rounded. We all know that muscle tone doesn't form like that, check this
for a reference image. Yes there is an almost round look to it, but you can make out the shape of the ribcage. I understand it is a cartoon but the roundness does not suit the semi-realistic nature of the image.
Also make sure you get your limbs in the right position, the arms do not overlap the chest - the chest flows backwards into the shoulders which become the arms. Also his lats should again join to the shoulder, the size you've drawn them at the moment makes him look more like a hunchback.
I'm sorry, I realise this is a really nit-picky critique, just take it as more of a complement that I have to look at these small details because you've covered the rest so well. You definitely have art skills in abundance, and your lighting and atmosphere creation are already far superior to mine, so please keep it up. But yeah my main advice is to try some still-life drawing and use more reference: I always try and find the animal that the pokemon is based on (because they usually are) in a similar pose, and work from that. Also if it strikes a more humanly pose then you can't go far wrong with using photos of gymnasts for referance, they have great and well defined muscle tone which makes the pose easier to see, as well as striking some pretty dramatic poses which make for great reference.