Here you can ask to have your oc or character play Quidditch/be a prefect, etc
Below I will tell you what's open and what's not

Gryffindor
Harry Potter - Quiddtich Captain and Seeker
Ginny Weasley - Chaser
Ron Weasley - Keeper and Gryffindor Prefect
Hermione Granger - Prefect
0/2 Beaters taken
0/2 chasers taken

Slytherin
Draco Malfoy - Quiddtich Seeker
Keeper - open
1/2 Beaters taken
1/3 chasers taken
Captain - Rosalyn 
Male prefect - Draco Malfoy
Female prefect - Pansy Parkinson 

Ravenclaw
Seeker - open
Keeper - open
0/2 Beaters taken
0/3 chasers taken
Captain - open
Male prefect - open
Female prefect - open

Hufflepuff
Seeker - open
Keeper - open
0/2 Beaters taken
0/3 chasers taken
Captain - open
Male prefect - open
Female prefect - open