Snape-centric prompts at The HP Friendship Fest
( There are several Snape-centric prompts still available that might interest you )
There are also a few "any character" prompts that seem to be made for Severus Snape. Why don't you have a look at our List of Prompts (on DW)? And if you found something to your liking, the prompt claiming post can be found here (and here on DW)!
Hope to see you over at hp_friendship/hp_friendship!