One possible storyline could be about Black Widow's escape from the tied - up situation. She might use her combat skills and intelligence to outwit her captors. For example, she could trick them into making a mistake and then break free.
Another storyline could involve her allies trying to rescue her while she is tied up. It could show the teamwork and the various strategies they employ to reach her and get her out of danger. Maybe they have to face some powerful enemies on their way to her.
A more complex storyline could be a love triangle between Black Widow, Spider - Man and another character, like Mary Jane. Black Widow might start to have feelings for Spider - Man as they work together on missions, but Spider - Man is still in love with Mary Jane. This would create a lot of drama and conflict within the fanfic.
One interesting storyline could be that they team up to take on a new villain that neither could defeat alone. This would show their combined skills and how they complement each other in combat.
Another storyline could be a time - travel one. Black Widow somehow gets sent to an alternate universe where she meets a younger Spider - Man. She has to help him understand his powers better while also trying to find a way back to her own universe. Along the way, they develop a deep bond.
There could be her fellow Avengers who might be involved. For instance, Captain America could be trying to rescue her, using his leadership and combat abilities. His sense of justice would drive him to save her from whatever danger she is in.
One interesting storyline could be a mission where Black Panther and Black Widow have to team up to take down a powerful international arms dealer. They could combine their unique skills, with Black Panther's enhanced strength and agility from the heart - shaped herb and Black Widow's spy training and combat expertise. Another could be a story set in Wakanda where Black Widow is sent on a diplomatic mission and she and Black Panther develop a mutual respect and friendship as they deal with political intrigue within Wakanda and threats from outside forces.
One common plot twist could be that she is tied up as part of a ruse by her own side. Maybe they are trying to deceive the enemy into thinking she's been captured. Another could be that she discovers a hidden power or knowledge while in this vulnerable state. For example, she might figure out a way to break free using some newfound skill she didn't know she had before. And sometimes, the person who tied her up turns out to be an old acquaintance with a complex backstory and motives that are not initially clear.
One possible storyline could be that Gohan and Black Widow are brought together by some sort of multiverse accident. They find themselves in a strange new world and have to rely on each other's skills. Gohan's superhuman strength and Black Widow's espionage expertise would make for an exciting combination as they face various threats.
I'm not sure specifically which 'Black Widow tied up' story on DeviantArt you're referring to. There could be various interpretations. It might be a story where Black Widow is in a hostage - like situation and has to use her wits and skills to escape. Or it could be part of a more complex superhero - themed adventure where she's captured by an enemy.
One interesting storyline could be Hawkeye and Black Widow on a mission before they joined the Avengers. They could be infiltrating a dangerous criminal organization, relying on their unique skills and their deep understanding of each other. For example, Hawkeye uses his archery skills to create distractions while Black Widow sneaks in to steal important information.
Perhaps a new, original villain created by the DeviantArt author. This villain might have some special powers or motives related to Black Widow specifically. For example, if the story is set in an alternate universe, the antagonist could be a powerful magic - user who ties her up using enchanted ropes to keep her from disrupting their magical rituals.