At least two photographs of Wilson exist, both in uniform, and both of which have been published. The most commonly known photo of him was published in 1906 as a frontispiece of a booklet written by Dr. Cyrus A. Peterson, who was president of the Missouri Historical Society at the time. If you want to track a copy down, that publication is entitled "Narrative of the Capture and Murder of Major James Wilson," a hard copy of which can be found in at least 17 libraries around the country. Microfilmed copies can be found in at least 32 libraries.
A second photo of Wilson was published in conjunction with an article I wrote entitled "The Burning of Doniphan," that appeared on page 82 of the vol. 6, no. 7 issue of North & South magazine in late 2003.
The first photo was posed by Wilson after he had obviously prepared himself ahead of time--no hat, hair combed and slicked back, well-kept appearance. The second photo appears to have been taken spur-of-the-moment and with Wilson fresh in from the field, as the kepi-wearing Wilson was fairly unkempt.