Haha, sometime I do want to adopt a mustang, I think they make great riding horses. Of course I'll want to get every single one I see when the time comes lol. I love that one with the ears, and just the little bit of color on the top of his head. Gorgeous.
About the lacing, it can be caused by one of two things that we know of so far, genetics, or a fungal infection such as rain rot. It's been proven in standardbreds that a certain stallion had the "gene" or whatever it is, and as he got older, the "pattern" got larger and larger until it finally reached his withers. If it's genetic, it generally starts on the top of the butt, and as the horse gets older, spreads up towards the horse's withers. It always stays just on the topline, never extends down the barrel. My tb had it, and as she was extremely well cared for and was only 8 when we got her, so we got her whole history, we believe it was genetic with her. Unfortunately I don't have any great pictures of it, nor do I have any documenting any changes over the 3-4 years I owned her. It definitely can be caused by rain rot though, and I haven't heard of the actual lacing pattern looking any different based on what caused it, so who knows how the mustang really got it. Still a neat "marking" though. Man, they have some nice looking mustangs. Gotta save up the money, get the land, and build the appropriate fencing to house one.