Using www. or not in front of the domain could depend on your audience. To be safe, prepend the domain with www. so there is no doubt.
I would recommend all lower-case for esthetics. I have made content for many large companies in the past involving their domain and so far there has been no exception to the domain being lower case (Europe, it may be different other places).
Consider a car used by a company which has "advertising" printed on it regarding the actual company.
In addition to this, why not add a QR code?
Keep the traditional (understandable by grand-paps and non-technical audience)
www.domain.com and add a QR-code for the more young, modern and enthusiastic audiences. With a QR code you can just point your mobile camera at it and go directly to the site it embeds (example below goes to wikipedia.org).
More on QR-codes