Does Dixit need any modifications to play with 7, 8, 9, and 10 players?
Dixit Odyssey has rules for 7+ players.  The suggested scoring system for 7+ players:


Each player has two vote tokens, not just one.  They can split their guess between two cards if they want.
If all players correctly identify the storyteller's card, or none do, everyone except the storyteller receives two points each.
Otherwise, the storyteller receives three points and so does anyone else who correctly identifies the storyteller's card.  If they only used one of their two votes, they receive a bonus point.
For each other card, the person who played it gets a bonus point (to a maximum of three) for each player who voted for it.


The game ends when the first player reaches 30 points.  Calculate the rest of the scoring for the round (in case someone overtakes), and then the winner of the game is the person with the highest number of points.