[color=magenta]It would be a good idea to get all of your Pokémon up around Level 45. Here are the Pokémon types that you will be up against when you take on the Elite 4.
Sydney: Dark types (Fighting/Bug types will work well.)
Phoebe: Ghost types. (Use Ghost/Dark attacks. She has 2 Banette, 2 Dusclops, and a Sableye. Sableye has no weaknesses, but it isn't all that strong either, just use your best against it. Watch out for her Pokémon's Curse attack too, if she uses it, you would be best off to switch Pokémon.)
Glacia: Ice, Water/Ice types. (Fighting/Rock attacks will work well against all of her Pokémon. Otherwise, use Electric attacks on her 2 Sealeo/Walrein, and Fire attacks on her 2 Glalie.)
Drake: Dragon types. (3 of his Pokémon have a 4x weakness to Ice, so a Pokémon with Ice Beam will have a pretty easy time against everything except for Kingdra, Kingdra is only weak to Dragon type attacks, so just go with your strongest attacks against it.)
Wallace: Water types. (Most of his Pokémon are dual-types, his only pure water type is his Wailord and Milotic. You will want both Grass and Electric attacks to cover all of his Pokémon. A Flying/Bug/Poison attack would be helpful against his very annoying Ludicolo. Whatever you do, don't let your Swampert get hit by Ludicolo's Giga Drain.)
Overall: Your team really doesn't need 3 water types, I would stick with Swampert and strongly consider replacing your Pelipper and Azumarill. Give your Swampert Ice Beam, and make sure that one of your Pokémon knows a good fighting type attack, like Brick Break. You could probably go with Mach Punch on Breloom, it only has 40 base power, but Breloom gets STAB from it, and it has a high attack stat. Brick Break would also go good with Swampert. If you replace your Pelipper and Azumarill with an Electric type and a Dark type/something that can use a Dark or Ghost type attack, you will be in great shape.