What you do is post this in one of the work-in-progress forums, probably Regional/World Building, and consider it the beginning of an amazing map. You're right that there are some amazing maps here, and some really great artists (in fact you have a reply from one already ), but there is also a lot of learning and practice going on. This community is really generous about providing feedback as you build your map, and I'd highly recommend trying that route out. As an example, I just posted this clunker, which is really not at all in the same league as your good start. But someday it will be good enough

That said, if you have a reasonable budget, chick's advice is spot on, and you will get some great results if you commission a map here. Especially depending on your time frame, you might not want to do a whole bunch of learning to create this map for your novel. You'll have lots of time when that's done to hone your skills.

cheers,
Meshon