You just edit the picture, or draw a totally new one. You can use paint or whatever, but it's usually 200x200. Then you host the picture on a site (imageshack, photobucket, xs.to, etc), then use this coding in your pet's description...

<style>div.pet {background-image: url(IMG URL HERE); background-repeat: no-repeat; width:200px; padding-top:200px} div.pet img {display:none}</style>

I use GIMP for my recolors, its a free download. Select the paintbrush, set opacity to 50 percent or so, and select 'colorize' as the option (as aposed to 'normal') then color away =)

=3 Just found this board, I'd like to check it out ^_^ I've never even heard of this o,O;