One possible reason could be for disguise. Maybe he is on a secret mission and doesn't want to be recognized easily. In the Naruto world, there are many dangerous foes, and wearing a face mask can help him blend in or hide his identity from those who might be targeting him.
Well, Deadpool's face in comics is quite distinctive. It's typically a mix of bold colors like red and black, and it's got those crazy eyes and a big mouth that's always ready for a wisecrack. Sometimes there are marks and scars to add to his rough look.
Under Qing Yunian's shadow mask was Great Grandmaster Sigu Jian's younger brother. The Shadow was the son of the former Dongyi City Lord, and he was the only survivor in the battle for the City Lord. He had been saved by Chen Pingping and had hidden his true face and identity. It wasn't until the 40th episode, when Fei Jie drugged him and took off his mask, that he discovered that he was Sigu Jian's younger brother.
Animal prints such as leopard or zebra are also trendy. They add a bit of wildness and fun to the mask. Abstract geometric designs are another option, which can be very modern and eye - catching.
There could be various time stories under the mask. Maybe it's about the time people spent hiding their true feelings during a difficult period. For example, during a war, people might put on a brave mask but have their own time - related stories of fear and hope in secret.
Definitely Naruto himself. Since it's a Naruto face mask fanfic, he should be the central character. His friends like Sasuke and Sakura can also be included. Sasuke could be jealous of the attention Naruto's mask gets, or Sakura could be the one to patch up the mask when it gets torn in a battle.