It's a sign - Original link:
http://www.runescape.com/l=3/img/main/kbase/controls/music_interface1a.jpg
And if Jagex takes it down:
rofl But still, the icons are a bit different. Aside from the obvious music icon, the Friends and Ignore icons are missing the hands. So this looks like an earlier image when they were still fine tunning the icons to the look they wanted. I still think it's possible that the sign could even be a simple placeholder image for when they are testing the use of the menu. They could have another image ready, one that actually reflects the use of the menu, but haven't placed it in the testing to avoid leaks like this. Then again, it could be that they're still designing the look of it. Although, there's still that chance that this could be what the icon is meant to look like. This image was found by manipulating a URL to an earlier version, so Jagex was obviously trying to hide a leak. They just didn't take it down from the server.
rofl Oh wait, they just did. Ha! Good thing I just screenied the image, rofl. But yea, if you change that image URL, the A to a B, that's after they removed the sign icon, but still had the older styles on the Friend, Ignore and Music. The current image up has a C at the end.
EDIT: Oh, and Twitter clue said: 'Some smooth moves are almost ready for RuneScape. Just in time as well, looks like those Fremennik are gonna need all them... Ajd'
Smooth moves = Tweening
Fremmy reference could involve the Aquanites. Especially with the "are gonna need all them" line. Kinda sounds like "Gotta catch'em all!", which people keep talking about how Aquanite sounds like a Pokémon.
rofl