HAH. A PCMCIA 16-bit card would be akin to installing an ISA card. A PCCard 32-bit would be like a PCI card. But of course they wouldn't be anything like a full ISA or PCI card, due to the space constraints for the size of the video chip, memory, cooling, et cetera. You might get maybe Riva128 power out of one.
Dell has a few laptops I think that allow a video card upgrade, via a mini-AGP slot. Whatever you buy now has the video in such a slot, and you just buy a replacement. I think they may be the only one. You'd have to get the full specifications or manuals for any laptop you want to check.