Sprite Stitch Board!

Hey everyone! I have lately fallen in love with the sepia look of patterns. There is an awesome Deviantart member who does custom sepia cross stitches and I wanted to try my hand in it as well. How would I go about converting a picture to sepia? And is it going to be hell to color match or would PCStitch/KGChart do a decent job given the limited shades of colors? I have a couple Vervaco projects in queue to stitch that have the sepia look, but I would love to make my own pictures. Here is a link to the person on DA who does it.

http://shingorengeki.deviantart.com/

And I nearly squealed seeing the Loki one posted now! I haven't looked back but I want to do that so badly! Please help.

Quick Edit: I wonder with the range of sepia-esque colors if it would be worth taking the time to just color match all of the shades as a universal reference? Or am I murdering myself to try that? Shingorengeki uses photoshop to edit...

Oh I know shingorengeki! She's awesome!
You should note her on dA and see if she has any tips on the monochrome / sepia pieces. She's really friendly so I imagine she may have some advice!

EDIT: Photoshop is the best way to do it, btw. I was gonna do a not-so-cool picture explanation but my pc just kinda had a funny turn and won't let me -_-