This has been brought up time and time again. Sims is the biggest contributor to xbooru and since there ARE ways to hide those images from showing for you if they annoy you so badly we as the staff will not be changing a thing.
Let me put it more bluntly. He benefits the website more then most other visitors, and if it annoys the vocal minority - that's not a reason for anyone to do anything because there isn't any issue to do anything about. (Yey for the English language...)