I believe DownUnderStables posted an answer to this Stable Name change trick a while back. Maybe he can assist with details again.

However it involved some advanced editing as I remember, not for PC newbies.

Download his Jockey/Trainer/Tipster Portrait collection also, an excellent job. Read his instructions on how to add your own trainer photo. Name file 141.bmp (must be 80 x 100 pixels)