Go to the quote button at the lower right of this post and you will see what I did to get this, 400 pixels high. You only want to do one dimension, the other will follow. Also, if you are going to use this in your signature, you are going to have to pare down the bytes, currently about 1 1/2 megs down to about 35 K. When forcing the image to look smaller (it really is not, just making it look so) you do not use the brackets [], but rather the greater than/less than <>, and the src code. Click on the quote and you will see. Also, only spaces here should be after the img, and after the 400.
<img height=400 src=http://home.comcast.net/~heidijot/scan.jpg>
BTW, VERY neat picture.