Probably SWF editing / Packet Editing & some emulator edits would allow you to get rid of it completely, unless you're looking to keep the friend aspect and just get rid of the bar it'd probably be the first 2 things I mentioned..
Youd have to edit the Habbo.swf XML. You could remove the image from the habbo.swf however it is used for more than just the bar. Can you show what it is exactly you would want removing?
There's no image for that one, you'll want to open the swf up in Leensters editor (
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) and find the layout bottom_background - I always just set width & heights to 0 incase I want them back at some point. Everything else on the bottom bars you'll find on layouts toolbar_view and new_bar