He might be very embarrassed. Howlers are known for delivering their messages in a rather loud and public way. Draco, who is used to maintaining an image of superiority, would find it humiliating to have his family's business aired out in front of his classmates.
Well, usually it leads to some intense drama and conflict. Maybe Draco gets scolded or given some important instructions.
It could be about Draco's performance at Hogwarts. Maybe Lucius is disappointed in Draco's grades or his behavior towards other pure - blood families' children.
He might be initially shocked. Draco is used to being the one in control and having others be intimidated by him. A Howler from Percy, someone he may not have considered a huge threat before, would be unexpected. He could be angry and vow revenge in his mind.
He'd probably be shocked at first. After all, getting a howler is quite embarrassing.
Perhaps another student, like Hermione, could send the Howler in a very creative twist in the fanfiction. Maybe she has found out that Draco is planning something malicious against the Gryffindors and uses the Howler as a way to threaten him into stopping.
Draco might immediately become defensive. He would probably try to shield Hermione from his father's wrath at first. He could also be filled with fear, knowing how strict and unforgiving his father can be.
Harry Potter can be an interesting character to pair with them. It creates a lot of conflict and potential for character development. Given their opposing stances in the original story, it can lead to some really intense and thought - provoking scenarios in fanfiction.
Voldemort might initially be furious. He's not used to being challenged in such a blatant way. He could try to destroy the Howler immediately in a fit of rage.
They could start by having an honest conversation. Lucius needs to admit his wrongdoings and Draco needs to express his pain. It's a first step towards redemption.
Well, in the vast world of fanfiction, it's very possible. Fanfiction gives writers the freedom to explore all kinds of scenarios, even the disturbing ones like this. But it's not something that is likely to be mainstream. The 'Harry Potter' fandom has a wide range of fanfictions, and while some may delve into this topic, others will stay away from it due to its rather grim nature.