Running OpenSuSE x86-64 12.3 (Dartmouth) - but I am not sure which exact version of KDE it is - best I can tell it is 4.10.5 (# rpm -qa | grep kde)
[EDIT] '# kde4-config -v' shows Qt: 4.8.4, KDE Development Platform: 4.10.5 "release 1", kde4-config: 1.0 [/EDIT]

In the "Kickoff Application Launcher" -> "Configure Desktop" -> "Display and Monitor" -> "Screen Locker" and <Screen Locker Type> is checked as "Screen Saver", there is the "OpenGL Screen Saver" that has an option for "GLSlideshow".

All it displays is a picture that looks like a color TV test pattern with a big red flame in the middle.
In the GLSlideshow "setup", there is no way to change the picture directory (eg: /home/<user>/Pictures/screen-saver) like there is in the "Banners & Pictures" -> "Slide Show".

A few web sites recommended creating a ~/.xscreensaver file with a single line: "imageDirectory: /home/<user>/Pictures/<picture_folder>"
Obviously I used my real home directory path and screen-saver folder.
I tried it, but it didn't change anything.

Is there a trick to getting openGL Screen Saver to use my screen-saver pictures folder?

Ok! I have it figured out!

But, I figured out how to get the OpenGL screen savers to work.
If you want to use the OpenGL Screen Savers, then you have to install the xscreensaver package (zypper install xscreensaver).
Then, run 'xscreensaver-demo' -
Be Careful! When a gray dialog box pops up warns you that the XScreenSaver daemon doesn't seem to be running on display ":0". Click <Cancel> - NOT <OK>

Now, there will be a Screen Preferences (XScreenSaver 5.20) dialog box with two tabs and some options.
In the "Display Modes", I picked "Only One Screen Saver" and picked "GLSlideshow".
In the "Advanced" tab, I selected the check box for "Choose Random Image:" and then my directory path to the folder.
Back on the "Display Modes", I clicked on "Settings". Now click on "Advanced" (lower left hand corner of the dialog box).
There will "Command Line:" text box at the top:
Mine reads "glslideshow -root -duration 60 -zoom 50 -pan 31 -fade 5"
Key to making this work reliably is to make sure that -pan < -duration value. If -pan > -duration, it seems to repeat the same picture several times before it changes - or it may never change.

Now, you can click on <OK>, and <File> "Quit".

Two things should happen:
In the "Kickoff Application Launcher" -> "Configure Desktop" -> "Display & Monitor" -> "Screen Locker", with the check box for "Screen Saver" and then scroll down to "OpenGL Screen Savers" and expand, then scroll down to "GLSlideshow", your preview should show the contents of your screen-saver picture folder.

And, when the time set in "Start automatically after:" minutes is reached, you slide show should kick in as expected.

Intuitively obvious.