It depends on what sort of suggestion. If you can run it past us then we might be able to point you in the right direction.
If it's a marketing strategy or idea for an event then the Marketing List might be good. Like all the other lists it is also widely accessible to the general public so anyone can comment. If it's an idea about languages then the L10n international translators list might help. If it's about UI design, themes or icon sets then Design Team. Lots of teams working on different aspects. TDF is quite large already.
Jay meant you can use the drop-downs in the bug-reporting thing as one of the drop-downs has "Feature request" listed soemwhere at the bottom
From: Jay Lozier <[hidden email]>
To: [hidden email] Sent: Monday, 26 August 2013, 21:41
Subject: Re: [libreoffice-users] Suggestions
On Mon, 26 Aug 2013 15:02:44 -0400, Jonathon Waterman
<[hidden email]> wrote:
> Where/who can you email a LibreOffice suggestion for improvement?
The easiest way is to file a "bug report" on Bugzilla and mark the "bag"