As a guy who has been playing Magic the gathering for over a decade I feel like your pieces lack the close up nature of the cards.
You seem to put everything in the mid/background.
Like the knight picture would be a close up of his face and horse.
The two people with the campfire would be a close up with a rocky surrounding and the mountains as a feint outlines.
The troll would be smashing/wielding a big club.
Sucking at something is the first step to becoming sorta good at something - Jake the dog