Often, PFPs featuring Sasuke with a determined expression or in a dynamic pose are in demand. Maybe it's because they convey his strength and personality. Also, those with high-quality art and vivid colors get a lot of attention.
Gon in fanfiction can be very single - minded in his pursuit of goals, just like in the original. He might be a bit more naive at times, which can lead to interesting plot twists. Killua is often portrayed as having a complex emotional side. He struggles with his past as an assassin and his loyalty to Gon. His cool exterior may crack in some fanfictions, showing his true feelings.
Sure. There was an artist who specialized in creating PFPs with a surreal and dreamy style. One of his PFPs got shared by a major digital art collector on a popular art platform. This led to a flood of requests for his work. He was able to sell many of his PFPs as limited - edition digital art pieces and made a name for himself in the digital art community.
Yes, there are likely some fanfictions out there with such a concept. Fanfiction writers often come up with creative crossovers. You can try searching on popular fanfiction websites like Archive of Our Own or Fanfiction.net.
I think Midoriya could be his best friend. Midoriya is kind - hearted and always looking to learn, which would appeal to Killua. They could bond over their shared desire to become stronger and protect others.
Often, they show a deeper level of commitment. The mpreg forces them to rely on each other more. For example, Gon might become more protective of Killua during the pregnancy.