This demonstration shows how jScrollPane can handle it when some slow loading images are included in the contents of the pane.
We use autoReinitialse so that the scrollpane automatically re-calculates the size of it's content if and when it changes. Note that use of this property adds an overhead to your page and is subject to the same warnings on the auto reinitialise demo page.
If you can it is better to include width and height for each image (either through width and height attributes or via CSS) in the markup. That way you can avoid the autoReinitialise cost. See this demo for an example of that approach.
The contents of this div will be replaced by the CSS added to this page