I don't know of any offhand here, but you'll get a lot of results if you search the web with terms such as ' how to make torn paper edges in photoshop ' etc etc. One of the results that popped up was this video tutorial on youtube: Photoshop: How to Make TORN or RIPPED PAPER Effect from Scratch. - YouTube which looks like it takes you through the steps to make a specifically positioned edge via selection, layer masking, and photoshop filters, etc. Another way I can think of which would give unique results and might work okay is tearing and scanning a piece of paper and using that as a brush/eraser or layer mask... It's a bit more involved though.

If I could make a small suggestion per your map parchment? With small islands dotted about everywhere, it's a lot better to use a background with only subtle variation in color and texture so that a) the piece doesn't become too busy to look at and, b) so the small bits of land don't get lost in the shuffle. That's said from experience :\ and a bit of regret. You might also consider giving more border space around the edge of your mapped area, with a neat line to contain the islands if you think it's appropriate for the look you're going for. Those are my thoughts anyway. Carry on. It does look promising.