I think by maps are too empty, he (she?) means that the rooms are too big, with too little in them. Say you have a room 700x500 px. And have 10 24x24 enemies, a chest, a couple of lanterns, and a few pots. and on each side of the room, you have a door. it would take too long for the character to move to every place. Most 2D zelda games don't have 6x6 units (whatever their using as a base block, i.e. LTTP had 16x16) of empty space, unless of course in a field or intentionally open area. In your screenshot, you have a hell of a lot of blank space.
Your view of 640x480 is too big, go with laigonaz, he knows what view dimensions to use.