What sort of body shape are you happy with? You have, with your requests, a fair few choices - but if we know what sort of snake you'd like we can make better suggestions.
If you're interested in slender, active snakes, try a corn or one of the european/asian rat snake species like the Russian Rats.
If you're interested in a heavy-bodied, slow snake, you're pretty much limited to royal pythons (and I don't personally think they're ideal for someone who's never had a reptile, though I can see you've got a couple and you're probably better equipped to deal with 'arrgh, won't eat!' than a complete reptile newbie).
If you want something heavy-bodied but able to be quick, maybe a Colombian Rainbow Boa or one of the dwarf boas would be good?
It also depends on how much money you want to spend, of course
