I was wondering if there any plan in the near future to add an sprite to julian or others npc without one and also is there a way for gunmar to stop being an asshole and behave more affectionate with the player?
Hyao has noted that he would eventually like to have sprites for everyone, they're just coming over time.
If you are submissive / a bottom, you can have a more positive relationship with Gunnar (although from what I've heard, that doesn't mean he's more affectionate per se!).
I will note, however, that you do have the opportunity to have some not-horribly-negative scenes with Gunnar provided you don't get a black heart with him - dual frotting with him, helping him with his shoulder injury as an herbalist.
It obviously will be a slow process, but there's definite room to at /least/ be friends for a mutually-a-top player, haha. I will personally consider it a victory if I can say 'hey' to him and have him nod at me and then go about his work grumbling.