The blue guy is an unreleased unit called the "Master at Arms."
This is a good time to shed some light on the design process. There are exceptions, especially when we're cramming before due dates, but we'll usually start with some very fast rough concept sketches and end up with something somewhat refined like this:
Then the design will get turned into a unit and a card:
(Sorry no card yet)
This unit was cut from Warlock Academy, which is why he's only half done. Also just because the unit isn't in the game, we have used them in other areas, such as Loremaster Tarius who makes an appearance on several Crusader cards.
A lot can change during these different stages of character creation, especially cards vs units on the lack of detail alone. It's an interesting, and fun challenge.
For example: take a look at professor head wood, his left forearm is twice as big as the rest of his arm and almost half the size of his belly mass.
The Professor's far arm is bent at the elbow, so he's hunched over and clutching the book to his upper body in a grade-filled rage. It makes it look like his arm is shorter.
Personally, I would start by drawing this:
Over and over again.
This image is a C&C equivalent to this:
Which is what many artists use to learn proper proportions.
It's funny because...
This exact card was made to design the proper character proportions for our game. We started with this image when we eventually developed our more strict style guide. Prior to this, even in my own work, proportion and style was all over the place. Even some of these design aspects have been dropped or exaggerated. I rarely use the wood on the Assassin anymore, because it's just not important and it distracts from the elements that are really important. We also don't render feet much anywhere. That one is just a style choice. Big heads, big hands, short torsos, short legs, spaced out eyes, no noses (except Brynjolf), and exaggerated eyes/mouths, are all important character design elements for us.
Cards and Castles' art direction is definitely rooted in modern computer illustration. It was originally, a very derivative style, looking like it could come right out of a Newgrounds game, but it has since evolved into it's own beast that requires a lot of love and care. We found a way to make flat characters and rigid animations fit the thematic elements, and that mostly revolves around a sense of humor that's hidden in everything we do. Grumpy ninjas, frat boy paladins, psycho pyros, iron throne imps, etc. There is meant to be a humor in their seriousness, because it fits the game. This game like any other competitive game has moments of epic heights and disastrous failures, with plenty of trolling in between. It's also a very fast game so we want our characters to bring some levity to the seriousness of deck building and strategic planning of tactical play.
As long as you start with the guide (proportions especially) and you have captured the feel, you should always go back to your work and exaggerate whatever can be exaggerated to push it more. Art, commercial or not, is full of intentional mistakes.