If you change the CSS height it expands vertically just fine:
modules/mod_ajaxscroller/mod_ajaxscroller/style.css
.ajaxscrl .mContainer {
width: 159px; /* edit this value for your own module width */
height: 124px; /* edit this value for your own module height */
display: block;
overflow: hidden;
position: relative;
}
.ajaxscrl .mScroller div {
display: block;
text-align: left;
margin: 0;
float: left;
width: 159px; /* edit this value for your own module width */
min-height: 124px; /* edit this value for your own module height */
}