Hi guys,
thought I'd drop in my .02 here as I've spent the last couple of months researching this to get cards made for my company.
Bicycle do indeed do custom cards, using the same stock and finish as their normal cards, fully customizable faces and backs with various options for boxes. The website states a minimum run of 10,000 decks, but if you email them or call them they'll generally give you a price for 5,000 as well - although they don't go lower than that.
Kardwell are good and the people are friendly, but I've had several sample decks and cards from them and their highest quality cards are nice but have very poor slip.
Cartamundi supposedly produce quite nice looking cards but so far I'm yet to see the samples they say they've mailed me (months ago).
PlayingCardsRUs are very helpful, and will send you custom decks if you're looking to get some made yourself, but again the best I got from them are very low slip.
I've finally settled with a company called Ad Magic. they've sent me a number of samples, and have been incredibly helpful and friendly. They have all sorts of options for card customization and box customization and they print using several different groups - including Gemaco. If it helps, Jeff McBride gets his cards made by gemaco (I *think* through ad-magic as well, although I can't remember if I asked him that). I have ended up going with a run of 1000 to get higher quality 300 GSM stock with a high slip linen finish, but they will definitely do much smaller runs for you.
The thing to remember about custom cards is most of these companies can make pretty much whatever you want in terms of look - where you're going to have trouble is the magic side of things. Even the best cards I've been able to get from admagic don't have the kind of slip that bicycle cards do, although having used them long enough to get used to them I find them fine now for magic. A lot of the other cards (especially all the plastic ones) just feel really poor quality in terms of magic use and fanning etc.
You may find that some of these cards are great for flourishing in the sense that they can be very strong and stay together well - for me the consideration was their use in everyday magic, as I will be using them all the time as business cards and performing magic as part of my work.
Ultimately I would choose bicycle if you can justify the expense (it's tax deductible for me, and obviously for any pro magicians) as the quality just can't be beaten - I'm moving countries in a year or so so I didn't want to get 10,000 decks with my phone number on that I'd have to throw away
When I move and am settled I will get a new run done through Bicycle.
If you have any questions about this sort of thing feel free to drop me a line too - I have quotes and sample cards coming out of my ears
Horus