You do NOT need to have your vehicle details and images to register, only the year, model and body style of your vehicle. You can add your vehicle details and images later after registering. In fact, it is recommended that you do NOT enter the vehicle description during registration.
A best practice is to write up details of your vehicle using a word processing app (e.g. Microsoft Word, Notepad, etc.), then copy and paste the contents for your vehicle after registering (under the "My Vehicle" tab).