I was surprised at the limited number of postcards at the hotel...but found a nice selection at the parks.
Easy to find postcards are the staples...Mickey, Minney, Princesses (in a group -- couldn't find postcards of them by themselves -- well, except for the Princess Pack -- but wasn't fond of those), Tinkerbell.
More difficult postcards were Nemo (found a postcard of the Nemo exhibit -- and used that instead)& Villains (never did find one).
You can definitely find SOMETHING that fits within the categories, just might not be exactly what was requested.
Either way, it was such a wonderful experience for me. I sent 8 cards -- and tried to get most of them done my first day there.