Hi Steinthor,
I hope it's not too late, but I was looking at exactly the same functionality to insert seismic lines and geological cross-sections. In fact, it's not that complicated, just a bit messy to play with.
The way I've found to insert vertical images is by defining a 3D marker symbol to a point. First off, you have to define an anchor point for your image you want to place vertically. Each vertical image you insert is a different shapefile. Otherwise each point will get the same image.
Once you have your anchor point, go in Edit Symbol and select 3D Marker Symbol. Import the image you wish to place (i recommend using rather low-res .png, otherwise it will be quite slow, especially with seismic surveys). Then edit the settings for the X Y Z and click Use Material Draping (see 3dmarker.png). Width (X) generally is the length of the line, while Z is your vertical depth (pretty useful to uncheck Keep Aspect Ratio if you wish to convert from time to meters).
In the 3D Placement Tab, you can edit (3dmarker2.png) where the image will anchor and its orientation. You have to play a bit with all these options as there are several ways to obtain the same result. One thing's sure, you have to uncheck "Display Face Front".
Hope it helps.
Christian Beaulieu
VIASAT GeoTechnologies
Montréal