This section is for both, except for models. Now, that means if you want to remake some runescape armor high res in Blender and render it out you are completely allowed to. But DONT post models created specifically for the runescape client here. The old models section has been renamed to “RS Models”
So making a dragon longsword in cinema 4d and rendering it out - Sure!
Making a dragon guitar SPECIFICALLY FOR THE CLIENT - No! Go to RS Models
You CAN have your own workshop thread and make client backgrounds for people, that is fine.
You CAN request a client background or banner.
You CAN make whatever you damn well please thats completely unrelated to anything and post it here 
This is just a general graphics section, have fun and learn lots!