There really aren't too many decisions that need to be made right now (for the order). The fuel senders is about the only true option on the wings, but even those can be left off and ordered later (if you weren't sure).
One other thing you may want to consider now is if you want the Deluxe fuel caps Van's sells. If so, you can have Van's exchange the standard caps for the order.
The lighting and all the other stuff can be decided at a later time, but it might be a good idea to at least start planning it out so you can drill neeeded holes while the wing is unassembled.
I posted a earlier thread with a similar question
here.
BTW... Dynon doesn't sell a heated pitot anymore (first one had issues). They have been working on it for a while, and are now saying don't plan on them releasing another one.
Correction: I just re-read the statement on Dynon's support forums about the heated pitot, they say they are still working on it, but will make no further claims as to when it will be released. Bottom line is, YOU may not want to plan on it. Sorry for the confusion.
Good luck!