Wow, it sure has been a long time since I saw that old theme. Not just the background, but the text of things like forum titles are blue instead of green. (If I remember correctly, we first saw green text as part of an April Fools prank by admin and founder Petrie, and we apparently liked the color change enough that we ended up keeping it.)
If we're going to start offering multiple themes, then perhaps the next thing we could try is the character featured in the read/unread icons. Currently, we're stuck with Petrie, and previously if we wanted to change that, it had to be an admin's decision. Perhaps with this new site, it might be possible to have all five of the main characters (or perhaps even more characters) be available and let us have the ability to chose whichever one we like.