The 4e DMG is clear on how much treasure, including magical treasure, to hand out per level by way of treasure parcels. 4e's math is balanced enough, however, that even going beyond this guideline won't throw it off too much. The main things to watch out for are bonuses to AC, NAD's, and weapons which the game assumes will scale at a given rate against monster attacks and defenses. You can generally be more "generous" with other items that don't provide those bonuses with little worry. I recommend staying away from cursed items. They can be frustrating to the players and don't bring much to your game (outside of nostalgia for past editions which is of little value in my opinion).