Christopher West was the artist for SWM maps. He now makes maps on his own and has maps that link together. I think you could link up to 8 maps at this point. Kind of pricey to get them all at once, but for the hours you would spend designing a map it's probably cheaper to just buy them.

Great question!
some maps and map assets were available as PDFs which you could then print out.
MoamirFarooq's maps were pretty awesome.
MapMaker and Shaper'n'Maker's maps were awesome also - they do the official maps and all, well worth it.

There are several custom maps elsewhere, such as on DevArt or BoardGameGeek,
they're not as balanced, but "Bounty Hunter's Refuge" is a nice generic map.

If you're wanting a quicker and easier way,
the scanning-pastiche way can yield okay results -
we used to do that for tile wars, before the locals switched to using Microsoft Visio/Adobe InDesign and finaldraftpro.
once you've laminated the map, you can hardly tell.
You want to ensure the map look alright at above 600DPI,
if you want to print it and have it look like the actual maps and all,
you could then take your scannings (assuming they're true CBYMK'd)
to a local printer,
and get em to print out on A2 or A1 ~180GSM Satin Semi-Gloss paper,
it will look a treat.
some printers will print the whole map on an A0 and cut to size, then stick that to the paper,
and it looks probably the neatest.

If you can only print at home,
check your manual to see if your printer can handle thicker cardstock,
as those tend to look nicest

Good luck, hopefully this was of some use to you
and you'll have to be sure to
share your results on the customs thread

Thanks for the excellent suggestions! Definitely some good starting points.