Centralian Carpets (bredli) get really big, but apparently can make good starter pythons.
As for womas, I can speak from personal experience. My first python was a woma and I would say they are close to perfect beginner snakes.
As already said there is a huge variety with in the species, for colour and size. The boodaries tend to be around 1.2-1.5m. Tanamis, RHD, sandfires, rabbit flats, etc are around 1.5m. Ulurus are around 1.8 and the SA's are over 2m.
All have different colourings with the boodaries and ulurus being darker with high contrast. The tanamis, sandfires, rabbit flats, RHD are lighter with a mixture of orange, caramel, reds and creams. The SA's are silvery with nice example showing a contrasting yellow or gold head. It's a personal preference as to what you prefer.
If you check out the last 10 or so pages of the ' show us your womas' thread, that should give you an idea of what is around and also who is expecting hatchies as there have been a few gravid, or possibly gravid females posted recently.
http://www.aussiepythons.com/forum/australian-snakes-37/show-us-ya-woma-s-126366/page/168
As for the reasons they make good starter is:
1. They like their food. Womas don't tend to go off their food. If you do a quick search you will see that a python not eating can be very stressful for a new keeper.
2. They don't have any special requirements and are very hardy. Shedding is generally not a problem, as they come from a dry climate.
3. They are known to be a placid species. Mine all so easy to handle.
4. They have a few 'special' quirks. Womas are famous for their tail wagging and head bobbing when excited. Two of mine do both, one only tail wags and the other only head bobs.
5. They make great Christmas presents. Most hatchies are available around Xmas time, so that gives you plenty of time to continue researching, set up a click clack, find a good hero vet just in case, etc before the new addition comes home.
Here are some useful links to look at.
The wiki on here is a good place to start.
Frequently Asked Questions - Aussie Pythons & Snakes
Snakey will need somewhere to live.
http://www.aussiepythons.com/forum/noteworthy-threads-5397/guide-build-click-clack-dial-93266/