Elemental swords, no. There are no such weapons in Naruto (excluding fillers & movies). Your own original Jutsu and kekkei genkai are allowed.
Example of things not allowed,
1) mechanical armors & equipments
2) mechanical weapons
3) tailed beasts with less than 1 or more than 10 tails. If you want to know why, please read the manga. Don't want to put the spoiler here.
4) max kekkei genkai per person, 2. If you want to know why, please read the manga. Don't want to put the spoiler here.
5) ghost, demons, or undeads.
6) immortality (no, even thou Hidan is immortal).
7) and of course abilities, powers, techniques from other anime.