I look forward to backing this again when you get it Kickstarted.
Some nice "stretch" goals, in my opinion:
* Upgrade from Bicycle to Aristocrat, from Aristocrat to Bee - or possibly get the variant Aristocrat that's used in the Tally Ho deck; they handle extremely well.
* Nowhere to go up on the finish... But you can upgrade the box. Embossing is a popular option, and another possibility is upgraded paper akin to what was used on the EATCT box (from CARC) or the black Bee Stingers (from Theory11).
* Metallic inks are always a fan favorite for a stretch goal.
* When reaching a good stretch goal, a bonus deck for orders over $X would work. Even better, an extra deck for every $X invested. Invest $X, get one deck more; invest $2X, get two decks; for $3X, get three extra decks, etc. This encourages more investment for the bonus decks, as long as $X is high enough to to keep you from getting creamed on the cost while not so high that it feels too hard to attain or too much in invest for just one bonus deck.
* Art prints, uncut sheets, posters: all make fine stretch goals or rewards.
* Free shipping is a nice stretch goal (domestic only). For international, give them a discounted shipping rate, and/or a higher stretch goal for free international shipping.
* Info, teaser posters, even a free deck - of your NEXT project - might be a good reward or stretch goal. This assumes you have another project to follow this up with, which I believe you do.
*Maybe offering the deck in more than one color as a big stretch goal would be cool. Perhaps you can make a red version, or green, or even yellow. It's better to offer extra colors up front rather than offering them as the "second version" deck, because then people moan about what a lack of originality a simple color change is - while secretly many of them would actually like more than one color! Two colors works great for creating poker gift sets!
* Some of the deck designers around here have been teaming up with a guy who designs bamboo deck clips with custom laser engraving - they're a good deal cheaper than any metal clip I've seen, and they should be excellent to use, so there's a possible reward/stretch goal. Offer plain ones as a reward or a reward add-on, then offer upgrades to custom engraved with Galvanic images as a stretch.
Most important thing before offering any reward or stretch goal - crunch the numbers and see if it works for you financially. You don't need to go totally over the deep end with the upgrades; just a small number with the appropriate stretch goals would be fine, I'm sure. If you go over your highest goal, there's nothing stopping you from creating a new stretch goal with a new bonus feature.
Another recommendation: many "first time deck makers" are realizing what a helluva chore the actual shipments can become. Poke around and see if you can find an affordable order fulfillment service to handle that end of the dirty work for you.
