If your White Kyurem EX is from Boundaries Crossed, you could pair it with Emboar (Black and White 20). Emboar can use Inferno Fandango to put Energy on White Kyurem EX each turn, so you can use Ice Burn consistently. You should also use Cilan (as a one-of) and Energy Retreival (3-4) to get Energy consistently. Victini EX can be used to power up White Kyurem early on while you're working on getting Emboar set up. For the ACE SPEC, go for either Computer Search or Crystal Edge. Computer Search gives your deck more consistency by searching out whatever you need to complete your set up or finish the game- Emboar, an Energy, a Rare Candy, a Switch, the game-winning Catcher- anything. On the other hand, Crystal Edge makes Ice Burn do a full 200 damage, which will OHKO anything with the exclusion of a Colorless EX with Aspertia and an Eviolite/ Large Cloak, which you won't encounter very often (unless your meta happens to be filled with those decks). If you can stream Ice Burns for 3 turns with this attached and take KOs only on EXs, then you can win the game quickly. However, getting Crystal Edge into play and keeping it there can be a challenge. As you can only play one, it becomes very vulnerable to being Tool Scrappered and Prized. If you want to have it in play at all times, Recycle and Town Map are very important. If you don't need it in play all of the time, you won't need to play as many of those cards, if any. Victory Piece isn't very helpful. The chance of getting it and Victini on the first or second turn, when you would use it, is low, it takes up your ACE SPEC slot, and you have the correct Energy for it anyway.
Skeleton list:
3 White Kyurem EX
4 Tepig
3 Emboar
1 Victini EX
11 Pokemon
4 Juniper
4 N
3 Skyla
1 Colress
12 Supporters
4 Ultra Ball
4 Rare Candy
4 Catcher
3 Switch
3 Energy Retreival
1 Super Rod
19 Items
8 Fire Energy
4 Water Energy
12 Energy
54 Total
So, provided I counted right, you have 6 slots left over. I didn't include the ACE SPEC because they take different cards to make them work. Other cards you can add are Pignite, Cilan, Emboar (BC) and Emboar (BW 19). Pignite and Cilan help consistency, while the other Emboars are non-EX attackers, for Klinklang and stuff like that.