I'm kind of leaning towards one red-pitcher plant, one dark-pitcher plant, and one spotted/speckled-pitcher plant. So maybe a ventricosa (or cross), a ramispina (or cross) and then some sort of spectabilis, maxima, etc... (or cross). Although, there are actually a lot more options for the speckled one too.
I've always been more partial to hybrids, so my suggestion would definitely be to look at some N. spectabilis and/or N. maxima crosses, especially the former. There are some killer crosses with N. spectabilis, and due to the N. spectabilis parentage are generally easy to cultivate successfully.
xvart.