hmm, i can't remember if there was an easier way to do it... there might not be a workaround, or at least, not one that i'm currently aware of.
as for layering images, i would probably make a style for it in your css node? so like
#character { margin-top: 200px; }
then in the story nodes:
<div id="character"><img src=""></div>
so it'd just be pure css, which you already know! or, of course, to save more time, you can create a separate node for each character and only have their div code in it, then call it within the main story:
node name: lys img
<center><div style="margin-top: 200px; background-image:url('filename.png');></center>
node name: generic story node
<<display "lys img">>
this should allow you to display different characters easily o