Yep, I think we asked for this a while ago...it still stands. For an interim fix, use the locations greasemonkey script in your browser which fades/grays out the locations you've already been to on the 'locations' page: beta.glitch.com/locations - not as effective as having it right on the map, but still useful.
I'd also like to see the maps correctly depict all the vendors and shrines. Especially in the newer areas like Alakol, many of them are missing. And it would be helpful for the greasemonkey script if the page descriptions for each street were accurate. Many of the Jethimadh are missing the vendors (I think Shimla Mirch too). Would also be nice to add which locations have the new dirt piles in the page descriptions (and I'm thinking the greasemonkey script could add this as yet another filter).