All depends on what you like and what you can afford. Take a look at some pics and read up on the genetics.
Here's NERD's BP page. Mind you, most of these are not in the average snake keeper's budget, but you can take a look at the base morphs (the cheapest ones, for the most part) and see what can be done with combos and such.
http://www.newenglandreptile.com/ner...ollection.html
Keep in mind that if you breed a recessive morph (albino, ghost, clown, axanthic, etc) to a normal, you will get normal babies and het babies, which look like normals but carry the morph gene. If you want to produce visual babies, get a dom or codom morph. (Spider, pastel, cinny, mojo, etc.)
(Personally, I LOVE spiders. Pastels are also great if you get a nice one. The problem is, most of the pastels out there are low-quality and dull with each shed. If you want a pastel, go with a baby that looks REALLY bright. Can't go wrong with a NERD lemon pastel.)