Suggestions

King : kings can be more than one with different abilities. The player can choose one of them based on his/her interest and deck and also can upgrade them like other cards.
-Ice king : slows down enemy's soldiers ( cards ) after 2 or 3 turns
-Flame king : makes fire on a part of the battlefield sometimes
-Super king : adds extra health or hit damage to the soldiers at the beginning of the battle
-Electro king : any enemy soldier that comes close to him will get electricized in a row of chain
-Fog king : stops or makes confused 1 or 2 enemy soldiers after 2 or 3 turns
2. More Maps : these five maps has become so stereotyped and boring. Please add 2 or 3 new maps
-Icy ground : a circle of ice exists in the middle of battlefield that slows down any card goes on it.
-Water tomb : has 4 fountains of water on 4 sides of the map that pour water to the battlefield ( not too long ) at the end of each turn. This water decreases the hit damage ( the damage caused by a card on the other cards ) or shield of any card that be in there and become watery ( just for the next turn ).
-Teleport field : has 4 holes on each corner that cards can go to one of them and exit from another randomly.
3. More Cards :
-Sniper : shots a lazer bullet that pass through enemy cards in a row
-Hunter : shots with a shotgun to his near area ( spread bullets )
-Crazify : makes one enemy card crazy ( like snowman ) when he/she hits it.Then, that card will go a direction different from what the player ( enemy ) has chosen in the next turn.
4. New Modes : 2v2
At the end I want to state one sentence. I hope you think deeply : This game has become like a Tv that shows the same movies everyday