Welcome to AP&S,
As MrSpike said, What sized python are you comfortable with, and then what do you like the look of, in that size range? There is no wrong answer, everyone has differant tastes, its just what you like and are happy with. Although, your 1st wont be your last lol.
As for carpets, Most are 8 foot and under Jungles, Inlands, MDs, Diamonds, Bredli, ect. but a Coastal can reach up to 12 foot, Ive included pics of my big boy 9 years apart.
Cheers Andy