I’d send them a wee short questioner asking for details such as colours/fonts/ tray/3D letters and even budget. And if they don’t fill it out artwork will be charged at £30 per hour for however many hours it takes and if doesn’t go ahead there will still be a bill. Big bug bear in office is when you ask questions and they reply with "just something that looks cool" or "something modern" so ask again and get sent the same reply or completely ignored and start telling you when they need it installed.
Write to them again, explaining you’re in the consultation period and no design has yet been started, hence why you’re now asking for their guidelines on what can and can not be used. Politely explain that you can’t just make up designs until you know what the customer wants or is allowed!