One common theme could be fixing past mistakes. Since they can time travel, they might go back to correct things that went wrong in their relationship or in Tony's technological endeavors.
I'm not sure specifically which 'peoper potts tony time travel fanfic' to recommend. You could try searching on popular fanfic platforms like Archive of Our Own. There are often a ton of fan - made stories there that might fit this category.
Love and loyalty are common themes. Their relationship is often shown as a deep, abiding love. Another theme is the balance between Tony's high - profile superhero life and Pepper's more grounded business role. Also, the idea of Pepper being Tony's rock, supporting him through his various crises.
Maybe in the fanfic, Tony uses time travel technology to go back in time to a moment before he met Pepper Potts. He then tries to avoid getting involved with her for some noble but misguided reason. However, his future daughter, who has knowledge of the 'right' timeline, comes back in time to set things straight and make sure her parents get together. She could be like a guardian of their relationship and the timeline related to it.
Love is a very common theme. Their relationship, whether it's the budding romance or the deep, committed love they share. Another theme is Tony's superhero life and how Pepper fits into it. She often has to deal with the dangers and the public attention that comes with it.
One common theme is loyalty. Pepper's loyalty to Tony is unwavering, and this is often emphasized in these fanfics. She will go to great lengths to keep him safe, whether it's from business rivals or super - villains. Another theme is love. Her protectiveness is rooted in her love for him, which can be romantic or just deep friendship. For example, she might stay up all night to make sure he's okay after a difficult mission.
One common theme is self - discovery. When Tony travels through time, he often has to re - evaluate who he is and what his purpose is. Another theme is fixing past mistakes. Since he's a brilliant inventor, he might try to use his knowledge to correct things that went wrong in the past. For example, in some fanfics, he goes back to prevent certain events that led to disasters.
She could be shocked at first. Pepper is a rational person, but time travel and suddenly having a daughter from the future or an altered timeline is a lot to take in. She might be hesitant to believe it at first, thinking it's some sort of trick or illusion.
Another theme is friendship development. Since Tony and Bucky start off on the wrong foot in the original MCU timeline. Time travel can throw them together in different situations where they have to rely on each other. This forces them to get to know each other better and form a bond that might not have been possible otherwise. For instance, in some fanfics, they are stranded in a time period and have to work together to survive.
A common theme could be family legacy. Since she's Tony Stark's daughter, there would be the pressure and pride of carrying on his name. Another theme might be self - discovery. She has to figure out who she is outside of being a Stark. For example, she might discover a passion for art or music that has nothing to do with her father's technological world.
Redemption is a common theme. Since Tony gets a second chance, he often tries to fix his past wrongs, whether it was a mistake in a relationship or a strategic error. Another theme is self - discovery. Through time travel, he gets to see different versions of himself and understand who he really is.