An excellent start indeed.
The tutorials here are probably your best bet. Some of this is deteremined by how good of an artist you are but even if you can't draw a lick you can get brushes from several sources that will allow you to pretty much stamp out a map. I know there are several members here who have posted brushes that are free to use.

The other thing, if you want the help, is to post up a Work in progress thread in one of the appropriate threads on this site. That will allow members to offer up suggestions on what you can do to make it better. Often times these wip threads end of up being the source of mini-tutorials on how to do specific things in photoshop or gimp, whatever.

So, if you want to keep working on this post it up in the Regional threads area and we'll see what we can do to help. Mind you it's been quite over the holidays but I'm pretty sure folks will be getting back into the swing of things now that it's a new year.