When you arm the system in STAY mode you are aware that your motions will not trip an alarm right? Based on that, when you're sleeping, you will be missing a lot of intrusion detection.
Don't forget wires for speakers - preferrable #16 or at least #18
How about a cable from the doorbell to your panel so you can do things when someone rings the bell?
I have a drive alarm which my wife highly approves of.
Consider rate of rise / fixed heat detectors in kitchen, attic, garage, furnace room, laundry. Locate one maybe 10' away from your fireplace flue in the attic.
Conside a CO detector or two
Even if you don't install all the sensros,
get the cable in now B)
Consider a keypad in your MBR - better to jump up and read that LCD message than to run through the house to look at the one in the entry during a burglar event.
I recommend #22 4/c cable to all sensors.
Plan on shunting the contact on the door from the garage to the kitchen when the GD is closed. This allows you to go in/out of the garage while the system is armed without tripping. I leave my garage door open a lot in warm weather and I can arm my system with it open and the screen door from the garage to the kitchen is then an entry zone which will trip if opened.
Run a cable from your GDO to the Elk panel - then you can make a rule to operate the garage door from any keypad. You can also have a F-key on the keypad blink when the garage door is open.
To save on keypads, if you care to, you can use a 4-button GE/ITI keyfob to arm/disarm your system as well as operate your GDO, turn inside lights on, etc. I consider them quite secure - but then I'm in a rural area without any interference. If you have children you want the keypads so you can have the Elk notify you when they disarm the system - if that's important to you. Keyfobs should be for adults - IMHO.
If you have glass panels on the sides of your doors you might want to investigate glass break detectors.
I second the suggestion to install smokes - even though code in your area lilkely requires 110v smokes - use 'em both.
If you have a gun cabinet, etc. run cable to them. If you will have an outside shed or something else you want to monitor get some cables to an outside junction box now.
Don't forget cables to your outside siren, strobe light, etc. And, you might decide it's nice to have outside indicators to show system status - armed/disarmed/alarm memory.
Good luck,
John