* Movement - I would rewrite the movement system so that the arrow keys move the player pixel-by-pixel instead of tile-by-tile. You can make it so that if the player walks into the corner of a block, he or she will instead move in a direction perpendicular to the direction that the player is pressing.
--Example: The player is pressing the UP key, but there is a block directly above the player so it is impossible to move in that direction. The player's x coordinate is smaller than the X coordinate of the block. Thus, the player's X coordinate is reduced pixel-by-pixel, step-by-step, until the player is no longer obstructed by the block, and the standard code for movement will allow him or her to proceed in an upward direction.

* Fire - When the player picks up a Fire Up item, it should not affect bombs that are already in play. When a player sets a bomb, and the bomb object is created, at that precise moment the player's Fire capacity stat should be passed to the bomb. When the bomb explodes, it will use its own local variable to determine the size of its explosion, rather than using the player's stat variable.

* Collision with Explosions - If a player is standing on a space that will soon be covered with a bomb's explosion, and the player moves off of that space right before the bomb explodes, the player will still die. I'm guessing that you are checking for collisions based on what tile the player was last on. This could be resolved if you implement a system that defines a mask for the player (a box with x1,y1,x2,y2 coordinates) and a mask for each explosion object, such that the player will only be affected by an explosion if his or her mask overlaps the mask of an explosion object.
--Example: The player's mask is currently (34,29,46,41). An explosion object nearby has a mask of (34,18,46,30). Since the player's mask overlaps the mask of the explosion object, the player will detect a collision with the explosion. (Note: the numbers given were just pulled out of thin air, there are probably better mask sizes for a Bomberman game and I can't remember what I've used in the past)

- If you have lot of power up's and are laying 2 bombs in a row not only one but more destructable walls will be destructed. Instead of 1.

- Most important.
You should set the bombtimer like 1 second longer if you want to play it competitive.
Play with the timer a bit to get it optimal.