I'd like to suggest a small cosmetic change. Here is a screenshot of how a typical thread looks on 1920x1080 (the height is cut in the image).
Maybe it's just my odd personal preference, but it would be great if the text area of the post used more of the screen width. In the image you can also see how the text on the bullet point list is constantly wrapping due to the lack of width (a common problem).
What to do?
For example, the lone post number and posting date information on the right (the green box in image) takes a chunk of the width. It could be moved on the left side, right above or under the author information. This would already open up more space horizontally for the actual post.
You might not like the next suggestion, but I would consider using the background image area on the left and right side of the screen for the text as well. I know you like the image, but it would still be visible in the list of topics! :-) Well, perhaps doing this would make the text area too wide? If so, maybe use only part of the former image area for the text.
Of course, these changes should be optional in the account settings. And while posting all this, I might as well suggest another display option for hiding signatures.
Thanks for reading. :-)