Oh BTW, this thread is already in the Regional Maps forum...(just in case you didn't notice). And I think those rivers do look a bit better arranged...
Well I think the resolution issue would depend on how much you want to be able to zoom in, and how good a graphics computer you have. At 1400x1600 px...
And we can show you how to do the same. :) Trust me. It is easier that you think with a bit of effort and some guidance that the Guild offers freely...