Angriff Railgun

Haha! I love the look of this piece. Skinny guy heaving a big hefty cannon with a smoking barrel and a pteradon-like creature of some sort falling toward the ground in a fiery mass.
I love the cityscape below the iron beam. To mean it says 'industrial metropolis', but with a cannon like that in view, it must be a 'industrial metropolis full of massive weapon manufacturers'.
I love how warm all the colors are in this piece, and how this are further represented in the pre-twilight sky.
The smoke, however, is dark and has solid lines. Smoke should have some dispersal, and, unless that creature is made of artificial materials, the colors should be much lighter. (synthetic materials burn dark, sometimes black. Organic materials burn with a lighter color, even if that material is still living.)
I'm not sure what was used as a propellant in the cannon, but if it's gunpowder or steam, you did good in deciding the color for it.
Finally, I like to focus on the Cannon Soldier. Everything is well with him, as I see no real flaw in his design. I even like the lollipop between his teeth.
All in all, while A few flaws exist, This is a great piece worthy to be put into the card game. I might even ask you to design sometging for my CCG I'm working on.
Maybe.