I was having this problem also and changing the css for the plugin didn’t work (noticed it was inactive after messing with it). I simply went in to my themes css and inserted the following code and it works great.
/******************************************
Comment Image Picture Control
******************************************/
.comment-image img {
max-width: 400px;
}
Of course just set the max-width to whatever looks good on your site. I hope this helps.
